Have you pray’d to-night, Desdemona?Desdemona. Ay, my lord.Othello. If you bethink yourself of any crime3330Unreconciled as yet to heaven and grace,Solicit for it straight.Desdemona. Alas, my lord, what do you mean by that?Othello. Well, do it, and be brief; I will walk by:I would not kill thy unprepared spirit;3335No; heaven forfend! I would not kill thy soul
This reminds of this scene in Hamlet when he didn't want to kill Claudius while he was praying. He hesitated to do so because if someone dies while praying, they are sent to heaven. Hamlet wanted Claudius to go to hell. This situation is a bit different here because Othello actually wants his wife to go to heaven so he's making sure she prayed before. It's somewhat nice and thoughtful even though he's about to kill her.