Musannaf Ibn Abi Shayba 33:298

Waki’ narrated to us, from Isma’il, from his brother, from Abu ‘Ubaydah, who said: ‘Abdullah said: "Whoever among you is able to place his treasure in the heaven, where the moth does not eat it and the thief does not reach it, then let him do so. For the heart of a man is with his treasure."