Musnad Ahmad 834:7

Waki’ narrated to us, from Abu Ja’far al-Razi, from al-Rabi’ ibn Anas, from Abu al-‘Aliyah, or from someone else, from ‘Abdullah ibn Mughaffal—and he was one of the group about whom this verse was revealed: {Nor [is there blame] on those who, when they came to you that you might give them mounts...} [At-Tawbah: 92] until the end of the verse—he said: I was holding a branch from the branches of the tree, shading the Prophet, peace and blessings of Allah be upon him, with it while they were pledging allegiance to him. They said: "We pledge allegiance to you unto death." He said: "No, but [pledge] that you will not flee."