Musannaf Ibn Abi Shayba 33:1319

Shadhan told us, he said: Mahdi ibn Maymun told us, from al-Jurayri, from Abdullah ibn Shaqiq al-Uqayli, who said: I heard Ka’b saying: "That I should weep out of fear of Allah, the Exalted, until my tears flow down my cheeks is more beloved to me than that I should give in charity the weight of my body in gold. By the One in Whose hand is the soul of Ka’b, there is no Muslim servant who weeps out of fear of Allah until a drop of his tears falls upon the earth, but that the Fire will never touch him, until the drop of rain that fell to the earth returns to where it came from—and it will never return."