Is it permissible for a person to abstain from getting married while he has the financial and sexual ability to marry?
This person is my friend. He claims that he does not want to marry in order not to produce children who may suffer the agonies of this world. He sometimes claims that he has become very old. Moreover, his mother wants him to get married.
Marriage is permissible in Islam. Increasing the number of the Ummah (nation) of the Prophet Muhammad is a desirable thing in Islam. The ruling of marriage differs according to one's circumstances. He who fears committing adultery if he does not marry has to get married if he is able to sustain his family according to the saying of most Fuqaha' (Muslim jurists). This is because being chaste is obligatory and the only way to be chaste is getting married. In this case, getting married takes precedence over performing Hajj. But if he is sure that he will not commit adultery, getting married in this case will be Mustahab (desirable). Therefore, if the reality is as you mentioned in your question, he has to seek Allah's help and search for a righteous woman in order to lead a chaste life and to make her (Part No. 18; Page No. 9) lead a chaste life also. Doing so will bring him benefits in this world and rewards in the hereafter. He should not say that he will not marry in order not to produce children who will suffer the agonies of this world. This is a false excuse that should not come to a Muslim's mind, let alone establishing rulings on it. May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.