Jim Kelly asked for prayers -- and Kurt Warner answered the call.
The Hall of Famer tells TMZ Sports he's friends with Jim and was devastated when he heard Kelly's oral cancer had returned.
"He's a godly man," Warner said ... "He's gonna find a way through this so I'm gonna continue to pray for him."
Kurt says he's already been in touch with the Kelly family to offer a personal message -- but encourages Jim's fans to keep up the prayers because he truly believes it helps.