Musnad Ahmad 555:2

Hassan ibn Musa narrated to us, he said: Hariz narrated to us, from Abd al-Rahman ibn Maysarah, from Jubayr ibn Nufayr, from Busr ibn Jahhash al-Qurashi, he said: The Prophet, may Allah bless him and grant him peace, spat on his palm and said: "O son of Adam." Then he mentioned its meaning.