Hassan (may Allah have mercy on him), the freed slave of Malik bin Abdullah al-Khath'ami (may Allah be pleased with him) - and Malik (may Allah be pleased with him) was one of the Companions of the Messenger of Allah (peace and blessings be upon him) - said: I saw Malik bin Abdullah (may Allah be pleased with him) performing ablution, and on his shin there was a vein on which "Lillah" (for Allah) was written. I began to look at it, and he said: "What are you looking at? Know that no writer wrote it."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16708