All perfect praise be to Allah. Blessings and peace be upon Prophet Mohammad and upon his family and companions.
Hajj isn`t incumbent on the minor who hasn`t reached puberty which is one of the conditions for the dueness of Hajj. However, a minor`s Hajj is valid and he/she receives the reward from Allah as mentioned in the sound Hadith: “A woman held up her child high and said: Messenger of Allah! Is Hajj due on him? He said: yes, and you receive a reward for it.“ {Moslim}.
Nevertheless, the validity of a minor`s Hajj doesn`t exempt him/her from performing it after puberty. This is because they are rewarded for offering it before puberty, but remains an obligation on them.
Ibn Al-Monzer (May Allah have mercy on him) said: “Muslim scholars agree that if the insane was accompanied to perform Hajj, and later he became sane, or if the child was accompanied to perform Hajj, and later he reached puberty; both aren`t exempt from the obligation of offering the Hajj.” {Al-Ijmaa`}(pp.212).
If your wife hadn`t reached puberty when she was twelve- she didn`t show signs of puberty such as: menstruation, wet-dreams, pubic hair- then performing Hajj is incumbent on her after attaining puberty, but if she had reached it, then nothing is due on her and so she doesn`t have to re-perform the Hajj. And Allah Knows Best.
