"Can I ask a favor? Can I pray for you?" would come across as very awkward if someone said that to me. It would just make me feel weird, as if you were trying to push your belief on me in a passive-aggressive fashion. I know it is meant with the best intentions, but personally, this is something I could absolutely do without in a time of personal crisis. So since we do not know much about OP's coworker, I would steer clear of that. — Cerno 1 min ago