Call upon Faith

Before attempting a difficult task, the priest may cast call upon faith to aid his performance. If the priest has been true to his faith (as determined by the DM), the priest gains a +3 (or +15%) bonus to one die roll (his choice) needed to complete the task. The bonus may be used to affect a saving throw, attack roll, ability check, etc. For example, if a priest were about to cross a narrow log high above a chasm, he could cast this spell and gain a +3 bonus to his Dexterity ability check.

[Tome of Magic]

Sphere: Summoning
(Invocation)
Level: 1

Range: 0
Components: V, S, M
Duration: 1 round
Casting Time: 1
Area of Effect: The caster
Saving Throw: None

Material Components:
the priest's holy symbol