Is the one who falls short in providing for his children sinful?

Question:
I have two wives; one is in Al-Aflaj and the other is with me in Riyadh. The one in Al-Aflaj has been ill for four years, and my eight children, who are young, are with her. Sometimes I send them money, and sometimes I do not, to the extent of my ability. Is there a sin on me for that?

Answer:
Yes, you must be just. You must be just. If you marry two, three, or four wives, you must be just. If one is in one country and the other in another, you assign days for this one and days for that one, or a month for this one and a month for that one, and so on, seeking justice. Likewise in financial maintenance, you provide for them according to their nature, equally. You fear Allah and strive to give them the obligatory maintenance. You do not give this one more because you love her and she is your companion. No, it is obligatory for you to be just between them. Yes.