Musnad Ahmad 2:228

Yazid narrated to us, he said: Asim ibn Muhammad informed us, from his father, from Ibn Umar, from Umar—he said: I do not know it except that he attributed it to the Prophet—he said: "Allah, Blessed and Exalted is He, says: 'Whoever humbles himself for My sake like this'—and Yazid placed the palm of his hand toward the earth and lowered it toward the earth—'I will raise him like this'—and he placed the palm of his hand toward the sky and raised it toward the sky."