I performed Hajj on behalf of my father from my husband's money, and when I returned, my father offered me a sum of money in return for the money I spent on Hajj. The sum he offers is greater than the money spent. Am I allowed to accept that money? Will this affect my reward or his reward? Is my husband allowed to take anything of that money?

All perfect praise be to Allaah, The Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Your Hajj on behalf of your father is valid and frees him of the obligation if he was unable to perform Hajj personally due to a chronic disease. As for the costs covered by your husband, if your husband gave the money as donation, do not take anything from your father. The Prophet, sallallaahu ‘alayhi wa sallam, said: "The one who takes back his gift is like the dog that swallows back its vomit." [Al-Bukhari and Muslim]

If he did not donate the money, but intended to get back what he spent on your father's Hajj, or intended that he would take back anything he spent so that he took what you spent during Hajj, you would be allowed to accept the money. That is because Hajj must be financed by the authorizer from his money which covers the expenses of the authorized as well. You should not accept the extra money because this would be like fees. Scholars differed about the ruling on taking fees in return for Hajj. Maalik and Ash-Shaafi‘i permitted it, whereas Ahmad, in the famous opinion of his school of Fiqh, did not. Furthermore, taking worldly compensation for the righteous deed diminishes its reward. It was narrated on the authority of ‘Abdullaah ibn ‘Umar that the Prophet, sallallaahu ‘alayhi wa sallam, said: "No group of fighters goes on a battle and takes booties but they hastened two thirds of their reward, where if they are martyred, they will achieve their reward in full." [Muslim] The Hadeeth indicates that accepting a worldly gain for a righteous deed decreases the reward of its doer, supposing its permissibility. This ruling applies when your father gives you that money in return for Hajj. However, if the money is a gift given to you or your husband later on, there will be no harm in accepting it at all.

Allaah Knows best.