The speaker decides in the second half of the poem that maybe he was hasty in calling for Judgment Day before knowing if he has been forgiven for his sins. He wants God to teach him how to repent, but repentance is harder than it sounds. One of the central Christian paradoxes is that people have already been saved by the death of Jesus Christ, but they can't be saved unless they come to faith by recognizing this sacrifice. The poem's complicated final simile grapples with this paradox.
- Lines 13-14: The last two lines introduce an important simile. Learning how to repent is like having the pardon for your sins sealed in blood. Donne conceives the pardon as an official document, the kind that would normally have a wax seal that serves as a kind of signature. But the simile is more complex than that. The speaker is saying that God really did seal his (the speaker's) pardon with God's own blood when He sent Jesus to die for the sins of humanity. The blood on the pardon is a metaphor for Christ's blood.