Musnad Ahmad 788:182

Yahya ibn Sa'id narrated to us, Qurrah ibn Khalid narrated to us, Humayd ibn Hilal narrated to us, Abu Burdah narrated to us, he said: Abu Musa al-Ash'ari said: I came to the Prophet, may Allah bless him and grant him peace, and with me were two men from the Ash'ariyyin; one of them was on my right and the other was on my left. Both of them asked for work, and the Prophet, may Allah bless him and grant him peace, was using a toothstick (siwak). He said: "What do you say, O Abu Musa—or O 'Abdullah ibn Qays?" He said: I said: By the One who sent you with the truth, they did not inform me of what was in their souls, and I did not perceive that they were seeking work. He said: It is as if I am looking at his toothstick under his lip, which had retracted. He said: "We do not appoint to our work one who seeks it, but go you, O Abu Musa—or O 'Abdullah ibn Qays." So he sent him to Yemen, then he sent Mu'adh ibn Jabal after him. When he arrived to him, he said: "Dismount," and he threw a cushion for him. Suddenly, there was a man with him who was bound. He said: "What is this?" He said: "He was a Jew who became Muslim, then he returned to his religion, the religion of evil, and became a Jew again." He said: "I will not sit until he is killed, the decree of Allah and His Messenger," three times. So he ordered him, and he was killed. Then we discussed the standing of the night (prayer), and Mu'adh ibn Jabal said: "As for me, I sleep and I stand, or I stand and I sleep, and I hope for (the reward of) my sleep just as I hope for (the reward of) my standing."