Musannaf Ibn Abi Shayba 36:83

Waki’ narrated to us, from Nafi’ ibn ‘Umar, from a man, from Abu Bakr, that when they reached the hole, he said: "If it is a hole," and Abu Bakr placed his foot over it. He said: "O Messenger of Allah, if it is a sting or a bite, let it be upon me."