Is it permissible to fast without praying?

Prayer is a fundamental pillar for the acceptance of fasting, and for one who abandons it, no deed is accepted. Al-Bukhari narrated that the Prophet, peace and blessings be upon him, said: "Whoever misses the Asr prayer, his deeds have been rendered vain." The meaning of "his deeds have been rendered vain" is that they became null and void and he gained no benefit from them.

Ibn al-Qayyim was of the view that abandoning prayer completely renders all deeds vain, while abandoning a specific prayer renders the deed of that day vain.

Shaykh Ibn Uthaymeen issued a fatwa stating that the fast of one who abandons prayer is neither valid nor accepted, citing verses and hadiths that describe the one who abandons prayer as an unbeliever, and based on the consensus of the majority of the Companions.

As for those who fast and pray only during Ramadan, the Permanent Committee issued a fatwa that their fasting is not valid given their abandonment of prayer outside of Ramadan, and by doing so, they are considered to have committed major disbelief, even if they do not deny the obligation of prayer.