Is the Hac of a child below puberty valid?

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