The moment you declare yourself to be religious or you made a choice of a religion for yourself which ideally should be after engagin in coparative study of religions, you declare your acceptance to a particular format of life. Religions believe in the Supreme power, God and religious people are expected to mould their conduct as per His teachings. Men and women are His creation. He chose to make man (unisex) male and female, and to give him the power, in partnership with himself, to produce new human life. Its God who is creating men so He has a say in reproductive act of which He has endowed the responsibility on men and women. So this makes sex sacred and holy.
To ensure the right use of the procreative power God founded the institution of marriage: the lifelong and irrevocable union of one man and one woman (in ideal circumstances but He has also provided us with the provisions to call it to an end in case of extremeties). The necessity of such a union is apparent, since it is essential not only that children be born but that they be lovingly reared and cared for by the father and mother who bring them into the world. Our juvenile courts and mental hospitals bear daily witness to the evils that follow when the unity and permanence of marriage are forgotten.

Marriage acts as an outlet for sexual needs and regulate it so one does not become a slave to his/ her desires. When sacredness of sex is lost then sanctity of marriage too disappears. It becomes a plaything, an instrument of pleasure than a diktat of God. Easy divorce and casual remarriages; prostitution and marital infidelity: these are some of the evils which follow when sex is twisted from its context in the divine scheme of things. No matter how selfless a couple may be, it is not easy for them to face the prospect of responsible parenthood, with all the sacrifices that entails. Especially it is not easy to face the prospect of an ultimate judgment, in which they will have to answer to God for the souls of the children who have been entrusted to them. It was God's instrument for the begetting, the rearing, the education, and the moral training of successive generations of human beings.

“And Allah hath given you wives of your own kind, and hath given you, from your wives, sons and grandsons, and hath made provision of good things for you. Is it then in vanity that they believe and in the grace of Allah that they disbelieve?” (16:72)

But it was not merely for the purpose of peopling the earth that God instituted marriage. Marriage is a religious duty and is consequently a moral safeguard as well as a social necessity. Islam does not equal celibacy with high "taqwa" / "Iman". The prophet has also said, "Marriage is my tradition who so ever keeps away there from is not from amongst me". It is a social necessity because through marriage, families are established and the family is the fundamental unit of our society.

Furthermore, marriage is the only legitimate or halal way to indulge in intimacy between a man and a woman. Islam takes a middle of the road position to sexual relations , it neither condemns it like certain religions, nor does it allow it freely. Islam urges us to control and regulate our desires, whatever they may be so that we remain dignified and not become like animals.
The word "zawj" is used in the Qur'an to mean a pair or a mate. In general it usage refers to marriage. The general purpose of marriage is that the sexes can provide company to one another, love to one another, procreate children and live in peace and tranquility to the commandments of Allah.

 Marriage serves as a means to emotional and sexual gratification and as a means of tension reduction. It is also a form of Ibadah because it is obeying Allah and his messenger - i.e. Marriage is seen as the only possible way for the sexes to unite. One could choose to live in sin, however by choosing marriage one is displaying obedience to Allah.

 Marriage is "mithaq" - a solemn covenant (agreement). It is not a matter which can be taken lightly. It should be entered into with total commitment and full knowledge of what it involves. It is not like buying a new dress where you can exchange it if you don't like it. Your partner should be your choice for life. One should be mature enough to understand the demands of marriage so that the union can be a lasting one."One of His signs is that He created for you spouses like your selves so that you may live with them with affection and mercy - there are signs in this for people who reflect." (Qur'an 30:21)

 This "sign" is the proof of the existence of a Creator. This is one of the biggest signs of Allah's existence: the physical differences and the mental make-up compliment each other like two halves of a whole, could not have come about without a Creator. A fact which disbelievers must acknowledge and in return, think of the purpose of their existence and submit to Allah.
 This is the background on purpose of marriage and why it is solely a religious bond. Its time for logical understanding. When one marries a person, may be, “MARRIAGE AS A VOW” he commits to be with him/her throughout life and take care of each other even when one enters in this bond in a registrar office or by ritualistic practices.
Here by marriage I am not concerned with signatory rights rather than something more deep which I have explained earlier. So, atheism which discards religious teachings and rejects guidance of the supreme and puts oneself on the path of a life which is free of any external restraint. You do what you feel necessary or right. Right?
You use your brain NOT mind because mind considers conscience which is not in existant for atheists. So atheists decide on basis of pros and cons of a situation using their brain to make a decision. Tell me what made you change your stands on your decided course of action? One day before you were shouting for free sex, one night stands, freedom to do anything and every thing until one day you experience a eureka moment and decided to show and celebrate your commitment to one partner for rest of your life which actually is teaching of religion.

“And God said: ‘O Mankind! Be dutiful to your Lord, Who created you from a single person (Adam) and from Him (Adam) He created his wife (Eve), and from them both He created many men and women.’” (Quran 4:1)

 So let me tell you, as this is a post on morality, religious morality prohibits us from entering into sexual experiences with random people outside marriage.

It since beginning demands us the commitment towards the one which atheists, after “enjoying” their lives of indiscipline want to appropriate, commitment to one. So what are you people doing? Cherry picking from religion to serve your ends? Marriage obviously provides you with social security but it is not it. It is deeper. Social security is an additional benefit of marriage and a secular one. Religion never appropriated marriage because marriage has always been a part of religion. So, at the end of the day atheists appropriate moral guidelines of religions and try to make it sound as their individual decisions. Yes those are your individual decisions but what is the source of these practices; obviously religion.

 You can say marriage has different meaning to different people but here we are not having timepass and proper discussions demand discipline, a set of rules. You can not enter into a tournament and shout I have my own definitions based on my thinking because I am an individual. You cannot b a part of an organisation with your rules and explanations. Objectivity in definitions are required. Atheists pick from marriages its social angle as those appear practical to them but they fear entering into a solid, concrete structure which will give them less scope for hanky panky. But once you decide for a thing you have to accept it whole.
Marriage is a truly ancient institution that predates recorded history .Today, the word 'marriage' is used by everyone including irreligious people who are not devoted to Allah, though it being a religious word. People get married, not because they have strong loyalty to Allah, but because society deems it necessary to start a family, or for other worldly reasons, even though disbelievers have no reasons to marry by the correct religious definition of the word.

Though marriage has ancient roots, until recently “love” had little to do with it. "What marriage had in common was that it really was not about the relationship between the man and the woman," said Stephanie Coontz, the author of "Marriage, a History: How Love Conquered Marriage," (Penguin Books, 2006). "It was a way of getting in-laws, of making alliances and expanding the family labor force."

 But as family plots of land gave way to market economies and Kings ceded power to democracies, the notion of marriage transformed. Now, most Americans see marriage as a bond between equals that's all about love and companionship. [I Don't: 5 Myths About Marriage].
That changing definition has paved the way for same-sex. This is how marriage which has been a religious practice is appropriated by different communities (homo, atheists) and there is an attempt to give marriage their own definition which obviously is vague, subjective, selfish and confusing.
When the person gives personal example to prove how committed he/she is even with Atheism

 Haha why are you getting personal? Did I ask you what you did with your husband or what you feel for your husband? We dont care what an atheist does but we care on what atheism permits and allows. Even if you had not experienced it personally but the moment you endorse a philosophy you directly agrees to its practices, whether you experience it for yourself or not is not our concern. So, what is better for you is to stick to the topic and make related comments, no timepass.
 We are talking on religion and atheism and at the same time keeping in mind the particular issue in discussion, morality. What I have said on marriage or what Waker  has said on faith, faults in evolutionary claims are all backed up by sources and logic. Yes it is debate forum so one has to come prepared. You cant keep saying you dont understand this and that, you have no idea about this and that. What are you presenting to be read is the main thing. I did not declare religious teachings to be superior I only presented to you what religion teaches and you on your own found and declared it to be superior of the two practices (You both come across as if you think you are superior because you have an invisible friend ) and I humbly accept your declaration on it. Yes guidelines from Him do make us feel privileged. Nothing to be jealous about. Lol.
 You have no time to read our "very lengthy comments" but you can make statements that "I think the pair of them have gone home quite shocked." We are here. We have been sharing with references. We are not talking in air. So we would expect the same from your side. We believe in religion so our texts are our proofs until you successfully prove them wrong. But alas, till date Science could not give the verdict with proper empirical sources on religion being bogus. 

I missed to add in my earlier comment on Hitler. I have already provided my source on his religious position being a matter of debate among scholars but the consensus agrees at his non-religious position. If I declare myself Christian do I become one or my conduct has to be a proof? When terrorists claim to be backed by Islam is that what Islam teaches? Obviously NOT so critical understanding of every topic is the must. 

Please make relevant comments. Take time if you need home work.