Sayyidah Aishah (may Allah be pleased with her) said: the Messenger of Allah (peace and blessings be upon him) said: "When any of you feels drowsy in his prayer, let him sleep until his sleep is complete, for when one of you prays while dozing, he may intend to seek forgiveness for himself but in reality be cursing himself."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4728
Sayyidah Aishah (may Allah be pleased with her) said that the Messenger of Allah (peace and blessings be upon him) said: "When anyone feels drowsy while praying, let him sleep on his bed, for he does not know whether he is praying for himself or against himself."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4729
Sayyiduna Abu Hurayrah (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "When any of you stands for prayer at night and the Qur'an does not come out properly on his tongue, so that he does not know what he is saying, let him lie down."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4730