It is narrated from Nu'aym bin Abdullah al-Mujmir that he said: One day I went up with Sayyiduna Abu Hurayrah (may Allah be pleased with him) onto the roof of the mosque. He was wearing trousers under his shirt. He pulled off his trousers, then performed ablution: he washed his face and his hands, washing his arms up to the shoulders and his feet up to the shins. Then he said: I heard the Messenger of Allah (peace and blessings be upon him) say: "Indeed, my Ummah will come on the Day of Resurrection with the limbs of ablution shining. So whoever among you is able to extend his brightness, let him do so."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الطهارة / 259