The Harness Divine Power optional feature from both the Paladin and Cleric class in Tasha’s Cauldron of Everything says the following:
You can expend a use of your Channel Divinity to fuel your spells.
It then goes on to say that you can touch your holy symbol as a bonus action to regain a spell slot, which you can do once per day, or more at higher levels, neglecting to say anything about using Channel Divinity. Does it require Channel Divinity, or not?
We must read the entire feature together. The first sentence says:
You can expend a use of your Channel Divinity to fuel your spells.
And so, the rest of the feature is telling us what happens when we expend a use of channel divinity to fuel our spells:
As a bonus action, you touch your holy symbol, utter a prayer, and regain one expended spell slot, the level of which can be no higher than half your proficiency bonus (rounded up). The number of times you can use this feature is based on the level you’ve reached in this class: 2nd level, once; 6th level, twice; and 18th level, thrice. You regain all expended uses when you finish a long rest.
