Section

On what the people of knowledge and faith, both earlier and later, uphold, which resembles the false doctrines of union and indwelling but is true—even if it is called indwelling or union. This is what Muslims, the people of the Sunnah and the community, and those possessing knowledge and certainty among all groups uphold, as evidenced by the Quran and Sunnah.

As for indwelling:

There is no doubt that when someone knows something, an impression and a quality arising from it must remain in his heart. His state after knowing it is not the same as his state before knowing it, as though knowledge were merely a relation, like being above or below. Someone who is above ceases to be above when he descends, and someone who is below ceases to be below when he ascends. Knowledge, however, does not disappear; rather, its effect remains in every case.

If, in addition to knowing it, he loves it, looks to it with hope, or fears it, these states produce a further impression and quality beyond knowledge and awareness, although the two may go hand in hand.

If he mentions it with his tongue, these effects become greater.

If he submits to it with the rest of his bodily faculties, this becomes greater still. In principle, these meanings are common to every perceiver and object of perception, everyone who loves and the object of that love, and everyone who mentions something and what is mentioned—whether this takes the form of worship, such as worshipping Allah