Narrated Ali ibn Abu Talib: A man of the Ansar called him and Abdur Rahman ibn Awf and supplied them wine before it was prohibited. Ali then led them in the evening prayer, and he recited; "Say: O ye who reject faith. " He was confused in it. Then the following verse came down: "O ye who believe! approach not prayers with a mind befogged until you can understand all that ye say.
Explanation & Benefits
Shaykh Umar Farooq Saeedi
Benefits and Issues:
Benefit: In prayer, a person should stand with full consciousness and attention.
Therefore, if someone is overcome by sleep during prayer, the ruling for him is that he should first complete his sleep.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 3671