Musnad Ahmad 30:1620

Mu'awiyah ibn 'Amr narrated to us, he said: Za'idah narrated to us, from Layth, from Ka'b, from Abu Hurayrah, he said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "You will be the bright-faced and bright-limbed ones on the Day of Resurrection due to the traces of ablution. So whoever among you is able to lengthen his brightness, let him do so."