Musnad Abu Ya'la al-Mawsili 160:222

Al-Qawariri narrated to us, Yahya bin Sa'id narrated to us, from 'Ubayd Allah bin 'Umar, he said: Sa'id bin Abi Sa'id informed me, from Abu Hurayrah, he said: The Messenger of Allah (ﷺ) said: "I had indeed intended to command the use of the siwak with wudu, and to delay the prayer until half of the night or until a third of the night."