Would the Life Cleric's Disciple of Life feature work with the Necromancer Wizard's Grim Harvest feature?

Question

The Life Domain cleric's Disciple of Life feature (PHB, p. 60) says:

Also starting at 1st level, your healing spells are more effective. Whenever you use a spell of 1st level or higher to restore hit points to a creature, the creature regains additional hit points equal to 2 + the spell’s level.

The School of Necromancy wizard's Grim Harvest feature (PHB, p. 118) says:

At 2nd level, you gain the ability to reap life energy from creatures you kill with your spells. Once per turn when you kill one or more creatures with a spell of 1st level or higher, you regain hit points equal to twice the spell’s level, or three times its level if the spell belongs to the School of Necromancy. You don’t gain this benefit for killing constructs or undead.

Would the Life Cleric's Disciple of Life feature work with the Necromancer Wizard's Grim Harvest feature?

For instance, if I’m due to get 8 HP from Grim Harvest for killing a mob with a level 4 Spirit Guardians spell, do I get an extra 6 HP thanks to Disciple of Life?

Answer 1

No

Disciple of Life:

...Whenever you use a spell of 1st level or higher to restore hit points to a creature...

In this particular instance you are using a class feature to restore hit points. Despite being a derivative from a spell's level the spell itself is not what is healing you. When you "use" spirit guardians, it is to deal damage. The spell is not used to restore hitpoints, and as such doesn't trigger Disciple of Life the way Cure Wounds or even Vampiric Touch would.

Answer 2

No, Disciple of Life only works with spells

Disciple of Life states:

Whenever you use a spell of 1st level or higher to restore hit points to a creature, the creature regains additional hit points equal to 2 + the spell's level.

Grim Harvest is not a spell, so it cannot trigger Disciple of Life.

Answer 3

Disciple of Life only works when a spell heals as part of its description, not when something outside the spell does the healing.

The Disciple of Life feature states:

[...] Whenever you use a spell of 1st level or higher to restore hit points to a creature, the creature regains additional hit points equal to 2 + the spell’s level.

The Grim Harvest feature states:

[...] Once per turn when you kill one or more creatures with a spell of 1st level or higher, you regain hit points equal to twice the spell's level, or three times its level if the spell belongs to the School of Necromancy [...]

Disciple of Life applies when you use a spell to restore hit points to a creature and Grim Harvest applies when you kill a creature with a spell. The question then is whether the healing from Grim Harvest (technically a result of casting the spell) activates Disciple of Life; whether this counts as casting a spell "to restore hit points".

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I would argue that no, it does not count.

This is because Disciple of Life requires you to cast a spell to restore hit points; not that you cast a spell, and that it just happens to result in the restoring of hit points; the spell must specifically be cast with the intention of restoring hit points. This is only the case if the spell's description states that it restores hit points, if the caster knows when casting the spell that it will restore hit points.

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If you had Disciple of Life work with Grim Harvest, it would also work when a spell pushes a creature into a healing aura/area

If you allowed Disciple of Life to trigger from Grim Harvest, where the spell is not directly causing the healing (it has to go through the Grim Harvest feature), you would also have to say that a spell that pushes a creature into a healing aura/area activates Disciple of Life. Here a spell is cast and it ultimately causes a creature to gain hit points by going through another feature (the healing aura/area), it would not be directly causing the healing.

I believe this is a more clear scenario that the answer should be (and is) that Disciple of Life does not trigger, and thus, it similarly does not trigger with Grim Harvest.