Sunan Abi Dawud 1311
سنن أبي داود#1311SahihNarrated Abu Hurairah:The Messenger of Allah (ﷺ) as saying: When one of you gets up by night (to pray), and falters in reciting the Qur'an (due to sleep), and he does not understand what he utters, he should sleep
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 Muslim (787)
In-book reference: 5:62