Al-Matalib al-'Aliyah 163 — One who warms himself with his wife

It is narrated from Ikrimah (may Allah have mercy on him) that "he saw no harm or religious difficulty in a man taking the bath for janabah and then (because of the cold) pressing against the body of his wife, who has not yet bathed, to get warmth; or in the woman bathing first and then clinging to the body of her husband, who has not yet bathed, to get warmth."
This report is established with an authentic chain, and it makes clear the juristic ruling that it is religiously permissible for one who has bathed to touch the body of a person upon whom ghusl is still obligatory, and it does not affect his purity.