What should one do who has no beneficial knowledge, no righteous child to pray for him, and no wealth with which to give ongoing charity?

One should utilize their life in obedience to Allah and in acquiring good deeds. The best acts of obedience are performing the obligatory duties, according to the hadith: "My servant does not draw near to Me with anything more beloved to Me than what I have made obligatory upon him." Then, one should increase in acts of worship that carry great reward. Scholars have differed regarding which of these is best after the obligatory duties: knowledge, or jihad, or prayer. Shaykh al-Islam Ibn Taymiyyah's view is that the superiority varies according to individuals and circumstances, and that these three are the best deeds by the consensus of the Ummah. Also, reciting the Qur'an has immense reward; for each letter, there are ten good deeds. Among the great-rewarding dhikr are the enduring good deeds (al-baqiyat as-salihat).