Is financial capability a prerequisite for marriage, and how sound is the hadith that mentions the Prophet, may Allah bless him and grant him peace, commanding a man who complained of poverty to marry? Also, what is better for a man who is stable with his wife: to be content with her or to marry another?

There is no disagreement regarding the permissibility of polygyny for one who is capable of providing maintenance and being just. As for one who is unable to provide maintenance, the Shafi'is and Hanbalis consider his marriage permissible, citing that the Prophet, peace be upon him, married off someone who owned nothing but a loincloth and an iron ring. The Malikis, however, deem it impermissible if it harms the woman due to lack of maintenance, unless the mature woman agrees to waive her right to maintenance. The hadith where the Prophet guides the poor to marry is weak. It is better for a man married to one woman, who has no need for another, not to exceed one, unless there is a need for a second marriage.