Is it obligatory for all of the deceased's children to participate equally in the expenses of Hajj on his behalf? Is it permissible for some of them to take money for this purpose from their affluent children? Does the reward include all of the children, or is it limited to those who contribute to paying the expenses?

A son is not obligated to perform Hajj on behalf of his deceased father. However, it is highly recommended and considered an act of filial piety after his death, based on the hadith of the woman who asked the Prophet, peace and blessings be upon him, "My mother has died and has not performed Hajj. Should I perform Hajj on her behalf?" He replied, "Yes, perform Hajj on her behalf." If a deceased person passed away after being able to perform Hajj but did not, and left behind wealth, then the heirs must allocate from his estate an amount sufficient for someone to perform Hajj on his behalf. Malik and Abu Hanifa, however, are of the view that the obligation of Hajj is dropped upon death. If the deceased made a bequest for Hajj, it should be fulfilled from one-third of his estate. There is no difference whether his son performs Hajj on his behalf or a stranger, whether for a fee or voluntarily. Everyone who assists in this, whether with money or effort, will be rewarded.