Hazrat Jaabir R.A. reports: “Verily Allah causes three people to enter into Paradise through one Hajj; The deceased, (on whose behalf this Hajj is being performed) the Haaji performing it and he (the heir or others) who makes possible its performance (by financial aid).”
Rasulullah (Salallaho Alaihi Wassallam) has said that when a person performs Hajj on behalf of another, he gets the same reward as the one whose behalf it is being performed. (Kanz)
Ibn Hazrat Muwaffaq R.A. says: “I have performed Hajj numerous times on behalf of Rasulullah Sal’am. Once Rasulullah (Salallaho Alaihi Wassallam) appeared in my dream and said: “O Ibn Muwaffaq, did you perform Hajj on my behalf?”
I replied : “Yes Rasulullah (Salallaho Alaihi Wassalam).”
Rasulullah (Salallaho Alaihi Wassallam) said: “and did you recite Labbaik on my behalf?”
I replied: “Yes Rasulullah (Salallaho Alaihi Wassallam).”
Rasulullah (Salallaho Alaihi Wassallam) then said: “On the day of Qiyaamat I shall repay you in full. On that day I shall take your hand and take you into Paradise while the rest of the people will continue to be reckoned with and called to account.” (Ithaaf)
Rasulullah (Salallaho Alaihi Wassallam) is also reported to have said: “A Hajj performed on behalf of another causes for four people to receive the reward of a Hajj; the one who made the wasiyyat (bequest) that it should be performed on his behalf; he who wrote down the testament; he who financed the Hajj and he who performed the Hajj.” (Kanz)
in case of Hajj-e Badal it is essential that the niyyat for performing Hajj on behalf of someone else should be sincere. The Haaji should have no aim other than to perform Hajj duties on behalf of someone else and to assist his fellow Muslim. Where other intentions enter into the picture, for example, where the Haji intends getting financial gain or other worldly benefit, that person on whose behalf Hajj is being performed will definitely get his reward, but the person who performs it , is deprived of the great blessing.
Hazrat Imam Ghazali R.A. writes that whoever perform Hajj for a fixed sum of money is actually selling his Deen for the sake of worldly gain. For this reason one should not make a special occupation of it, because in rewarding us for our Deen (religious activities) Allah often grants us worldly wealth and power as well. But by selling the Deen our worldly wealth does not increase. Allah certainly does not grant us Deen in return for worldly activity and gain.