Sunan Abi Dawud 2448
سنن أبي داود#2448SahihAbd Allah b. 'And (b. al-'As) said:The Messenger of Allah (ﷺ) said to me: The fast most liked by Allah is the one observed by Dawud (David), and the prayer dearer to Allah is the one offered by Dawud (David): he would sleep half the night, and stand (in prayer) one-third of it, and sleep one-sixth of it. He would go without fasting one day, and fast the other day
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniSahih
Muhammad Muhyi Al-Din Abdul HamidSahih
Shuaib Al ArnautSahih
Zubair Ali ZaiSahih Bukhari (1131) Sahih Muslim (1159)
In-book reference: 14:136