Musnad Ahmad 27:141

Sufyan narrated to us, 'Amr narrated to us, from Abu al-'Abbas, from 'Abdullah ibn 'Umar—it was said to Sufyan: "Ibn 'Amr?" He said: "No, Ibn 'Umar"—that when the Prophet, peace and blessings of Allah be upon him, besieged the people of Ta'if and could not attain anything from them, he said: "We are returning tomorrow, if Allah wills." It was as if the Muslims disliked that, so he said: "Go forth [to fight] in the morning." So they went forth to fight in the morning, and injuries afflicted them. Then the Messenger of Allah, peace and blessings of Allah be upon him, said: "We are returning tomorrow, if Allah wills." The Muslims were pleased, and the Messenger of Allah, peace and blessings of Allah be upon him, laughed.