Question

After my brother had previously performed Hajj for himself, he performed another Hajj on behalf of my deceased father. It is known through authentic Hadeeths that the one who performs Hajj without approaching his wife for sexual relations or committing disobedience therein will return as free from sin as the day his mother gave birth to him. It is also reported that the reward of an acceptable Hajj is nothing but Paradise. Would this reward include the one on whose behalf the Hajj was performed, meaning my father? Noting that he was known for his righteousness, faith and obedience but could not perform Hajj during his life.

Fatwa

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

If a person died before performing a Hajj that was due on him and was unable to perform Hajj, then the closest of his kin should perform it on his behalf. Both the deceased and the one who is unable to perform it would receive the reward of Hajj, if Allah wills. This is because the Hadeeths that encourage the performance of Hajj give a general indication, which encompass the one who performs the Hajj himself as well as the one on whose behalf it is performed. Among these Hadeeths is the one that reads: "The one who comes to this House so as to perform Hajj and neither approaches his wife for sexual intercourse nor commits disobedience will be as free from sin as he was on the day his mother bore him." [Al-Bukhari & Muslim]

Hence, your brother did well when he performed Hajj on behalf of his deceased father as he is actually required to do so based on the Hadeeth narrated on the authority of Ibn ‘Abbaas, may Allah be pleased with him and his father, who said that, "A woman from the tribe of Juhaynah came to the Prophet (may Allah exalt his mention), and said, 'My mother vowed to perform Hajj but died before performing it. Should I perform Hajj on my mother's behalf?' The Prophet replied: 'Perform Hajj on her behalf. Had there been a debt on your mother, would you not have paid it? So pay the debt of Allah as He has more right that one should fulfill his obligations to Him.'" [Al-Bukhari & Muslim]

It is also narrated on the authority of Ibn ‘Abbaas, may Allah be pleased with him and his father, that he said, "A woman from the tribe of Khath‘am came in the year of the Farewell Pilgrimage of the Messenger of Allah and said, 'O Messenger of Allah, the obligation of Hajj became due on my father when he was very old and could not maintain his balance on his mount (due to his old age). Will the obligation be fulfilled if I perform it on his behalf?' The Prophet replied in the affirmative." [Al-Bukhari & Muslim]

If your father did not perform Hajj because he was unable to, then he is not sinful, if Allah wills.

Allah Knows best.