Answered by Shaykh Yūsuf Badāt
Does sleeping during a fast invalidate the fast (sawm)?
In the Name of Allāh, Most Merciful, Most Compassionate
Jazak Allāh Khayr/ Thank you for your question.
Sleeping while fasting does not islamicaly invalidate the ritual fast, as this does not entail any substance entering the internal mind or stomach cavity.
Ibn Abbās (may Allāh be pleased with him) and Ikramah (may Allāh be please with him) have stated, “The fast is invalidated by what enters the internal stomach cavity.” (Bukhārī)
“There is no negligence in sleep. Negligence is by the person who does not pray [mandatory ritual prayers].” (Ṣaḥīḥ Muslim)
Excessive sleep during fasting is considered makrūh (disliked) as it deprives one of the opportunity to carry out good deeds.
And Allāh Knows Best