Is the Haji of a child below puberty valid?

A child's Haji is valid as a voluntary act of worship (nafl), but it does not fulfill the obligation of the Haji of Islam. When the child reaches puberty, they must perform the wajib Haji again. This is based on the hadith of Ibn Abbas: 'A woman lifted a child and asked: Is there Haji for this one? Nabi (shallallahu alaihi wa sallam) said: Yes, and you will have a reward' (Sahih Muslim 1336). Sheikh Ibn Baz stated: 'The Haji of a child is valid as nafl but does not count as the wajib Haji' (Fatawa Ibn Baz, vol. 16).