Musnad Ahmad 788:238

Hassan ibn Musa—meaning al-Ashyab—narrated to us, he said: Sukayn ibn Abd al-Aziz narrated to us, he said: Yazid al-A’raj informed us, he said: Abdullah—meaning I think he is al-Shanni—said: Hamzah ibn Ali ibn Makhfar narrated to us, from Abu Burdah, from Abu Musa, who said: We went on a military expedition with the Messenger of Allah, may Allah bless him and grant him peace, during some of his travels. He said: The Messenger of Allah, may Allah bless him and grant him peace, halted with us [to rest] at night, and I awoke during part of the night looking for the resting place of the Messenger of Allah, may Allah bless him and grant him peace, but I did not find him. He said: So I went out into the open looking for him, and behold, there was a man from the companions of the Messenger of Allah, may Allah bless him and grant him peace, looking for what I was looking for. He said: While we were like that, the Messenger of Allah, may Allah bless him and grant him peace, turned toward us. He said: We said, "O Messenger of Allah, you are in a land of war, and we do not feel secure for you. If only, when you had a need, you had told some of your companions so that they could stand with you." He said: The Messenger of Allah, may Allah bless him and grant him peace, said: "I heard a humming like the humming of a millstone, or a yearning like the yearning of bees, and one came to me from my Lord, the Mighty and Majestic. He said: He gave me the choice between having one-third of my nation enter Paradise and [having] intercession for them, so I chose my intercession for them, for I knew it was more expansive for them. Then He gave me the choice between having half of my nation enter Paradise and [having] my intercession for them, so I chose my intercession for them, for I knew it was more expansive for them." He said: They both said, "O Messenger of Allah, supplicate to Allah the Exalted to make us among the people of your intercession." He said: "So he supplicated for them." Then they alerted the companions of the Messenger of Allah, may Allah bless him and grant him peace, and informed them of the statement of the Messenger of Allah, may Allah bless him and grant him peace. He said: They began coming to him and saying, "O Messenger of Allah, supplicate to Allah the Exalted to make us among the people of your intercession," and he would supplicate for them. He said: When the people crowded upon him and became numerous, the Messenger of Allah, may Allah bless him and grant him peace, said: "It is for whoever dies while testifying that there is no god but Allah."