Musnad Ahmad 33:20

'Abd al-Razzaq narrated to us, Ma'mar narrated to us, from al-Zuhri, from Abu Salamah ibn 'Abd al-Rahman, from Jabir ibn 'Abd Allah, who said: "The *'Umra* (life-gift) which the Messenger of Allah, peace and blessings of Allah be upon him, permitted is for a man to say: 'It is for you and for your descendants.' As for when he says: 'It is for you as long as you live,' then it returns to its owner."