My husband and I went to Hajj and the day we were on Jabal Arafat my husband put a towel on his head unknowingly. Does he have to kill a goat as Kafara (expiation) for that? Please advise us.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.

If the matter is as you mentioned in the question, then your husband is not required to do anything as he covered his head out of forgetfulness, and a forgetful person is not obliged to offer a sacrifice in such cases. The Prophet said: ''Allaah has forgiven my nation for things they forget, or do by mistake, or which they are forced to do.'' [Ibn Maajah & Al-Bayhaqi]. 

Allaah Knows best.