Is it mandatory to have kids after marriage? What is the ruling on this in Islam?
I am asking this question in terms of couples who are perfectly healthy and can have babies but still choose not to have one their whole life.
In many places, Quran says children together wealth, like
Wealth and children are [but] adornment of the worldly life. But the enduring good deeds are better to your Lord1 for reward and better for [one's] hope. Quran 18:46
But just like there is no wrong in earning wealth in allowed (halal) ways, there is nothing wrong in trying to have good children. Actually in Quran, you can see it is always recommended to always pray for righteous children
And those who say, "Our Lord, grant us from among our wives and offspring comfort to our eyes and make us a leader [i.e., example] for the righteous." Quran 25:74
Also, it is not right to not have children fearing poverty. During pre Islamic period, infanticide was popular fearing poverty.
Do not kill your children for fear of poverty. We provide for them and for you. Surely killing them is a heinous sin. Quran 17:31
Having righteous children who will pray for you is one of the 3 things that do not stop even after your death.
The Messenger of Allah (ﷺ) said, "When a man dies, his deeds come to an end, except for three: A continuous charity, knowledge by which people derive benefit, pious son who prays for him." https://sunnah.com/riyadussalihin:949
So it is always recommended to try and pray to have righteous children and it cannot be said as mandatory. Because for some people Allah will not grant children even if they try.
Or He bestows both males and females, and He leaves barren whom He will: for He is full of Knowledge and Power. Quran 42:50