Musnad Ahmad 337:7

Yahya ibn Ishaq narrated to us, Ibn Lahi'ah narrated to us, from Habban ibn Wasi', from Khallad ibn al-Sa'ib al-Ansari: "That the Prophet, peace and blessings of Allah be upon him, when he would ask [supplicate], he would place the palms of his hands toward himself, and when he would seek refuge, he would place the backs of them toward himself."