Musnad Ahmad 189:1

Abu al-Nadr narrated to us, he said: Abu Mu'awiyah—meaning Shayban—narrated to us, from Yahya ibn Abi Kathir, from Yahya ibn Ishaq, from Mujashi' ibn Mas'ud, that he brought a son of his brother to the Prophet, peace and blessings of Allah be upon him, to pledge allegiance to him for migration. The Messenger of Allah, peace and blessings of Allah be upon him, said: "No, rather he shall pledge allegiance for Islam, for there is no migration after the Conquest, and he shall be among those who follow in goodness."