Is it permissible to wipe over the head during ablution while there is gel or any hair styling product on it, knowing that the Messenger of Allah (peace be upon him) used to put a gum-like substance on his hair when in a state of Ihram? And what is the ruling on this for someone afflicted with obsessive-compulsive disorder (OCD) who delays prayer because of it?

It is authentically established that the Prophet, peace and blessings be upon him, matted his hair during the Farewell Pilgrimage. Matting the hair means gathering the hair of the head with a substance like gum during the state of Ihram (definition). Some jurists permit wiping over matted hair for a person in Ihram due to necessity. Modern gel is not analogous to matting the hair for Ihram. Gel is applied for adornment and may involve imitating disbelievers. Furthermore, gel may contain unslaughtered animal gelatin, rendering it impure, and it must be removed for Wudu (ablution). It is preferable not to use gel, and whoever uses it must remove it for Wudu. Some scholars have permitted wiping over hair matted with henna or gum, by analogy with the Prophet's matted hair, especially since the purification of the head is based on the lighter ruling of wiping.