The Nikah or marriage is an act of worship which Allah has designated for mankind to multiply and regenerate.
Allah says:

O Mankind! Fear your Rubb Who created you from a single person and created from it its mate, and from both He multiplied many men and women.¹

Islam regulates and canonizes marital relationship to ensure reciprocal and mutual love and respect between the couple. The Prophet, may Allah exalt his mention, encouraged the youth to get married saying:

Young people! Whoever of you can afford it, let him get married, for marriage helps restrain the eyes,² and preserve chastity. He who cannot afford it, let him observe fasting, for fasting is as effective as castration is.³

The Purpose of Marriage
Allah says:

And among His signs⁴ is that He created mates for you from among yourselves that you may find comfort in them, and has made love and mercy between you. In that surely are signs for people who reflect.⁵

It is equally important for a man to choose the religious woman for a wife as it is for a guardian to choose a religious man for his female dependent.
The Prophet, may Allah exalt his mention said:

A woman is chosen for a wife for four reasons: Wealth, family lineage, beauty or piety. You should marry the religious.

He also said:

‘When a man with whose religious standard you are satisfied, proposes your daughter give her to him. If you do not there would be adversity on earth and great corruption.’ ⁶

The corruption against which the Prophet, may Allah exalt his mention, warned would be brought about by giving one’s daughter to an irreligious man who would not raise his children as good Muslims, hence increasing the number of irreligious people in the community.
The Messenger of Allah, may Allah exalt his mention, defined the good wife as:

The woman whom when you look at her, she pleases you, and when you command her, she obeys you, and when you insist on her to do something, she fulfills your wish and when you leave her behind, she guards herself and your property.