Peace be upon you. What is the meaning of ḥulūl (indwelling) and ittiḥād (union)? May Allah reward you.

The beliefs of hulul (divine indwelling) and ittihad (divine union) are both disbelieving doctrines. Hulul is the belief that Allah indwells in some of His creations and unites with them, such as the Christian belief in His indwelling in Christ, and some Sufis' belief in His indwelling in Al-Hallaj and others. As for ittihad, it is the belief that the essence of creation is the very essence of Allah Almighty, which they call wahdat al-wujud (unity of existence). Adherents of this doctrine believe that the existence of the Creator is identical to the existence of creation, and that all qualities, good or bad, attributed to creation are, in their view, attributed to the Creator Himself. For them, the Creator has no existence separate from creation. Among their outlandish claims is that they consider idol worshippers to have worshipped none other than Allah, and that Pharaoh was correct in his claim of divinity and died as a believer.