In Arkham, we know that faith can keep us sane. The Holy rosary is one of the few zero xp sanity adding assets. But you can throw that on for one action before leaving the house. The book of Psalms is going to take us more effort. This is a support card. Generally, it’s not useful to take two actions to heal one damage or horror. (every healing asset requires us to put in a play after all.) Every three actions you take, generally, the encounter deck is going to drop more problems on you. Which means we need other reasons to play this.
First, we could be a therapist. Carolyn, being at the top of medical science in the 1920s, is willing to use Hypnotic Therapy and prayer. She gets a buck and can heal one or two san while adding bless tokens to the bag. Super effective: 8 bless tokens and a net profit for the team.
Second and more obviously, this is useful for a support Mary or Mateo. Most of the Conspiracy investigators have good sanity, Silas has five. Keeping him alive while you feed the bag plays into the support archetype.
Least obviously but most thematically interesting is taking this card with Joe or Roland. As blue/yellow investigators, they can take Astounding Revelation...and discover secrets in the writings of King David! The idea of secrets in the Psalms may make money indirectly, because people are still publishing books to that effect more than 100 years later.
Which is enough to cause you sanity damage.