It is the Lord himself, who grants mercy. God is righteous, just, and must punish sin. He will not deny himself, but he has made a way to satisfy the wrath of those who will put their trust in him. On the cross, we see the wrath of God propitiated for those who will come to him in faith. When the triune God saw the problem of sin in his people, he took it upon himself to provide the needed mercy.
May the Lord grant him to find mercy from the Lord on that day. – 2 Timothy 1:18
There is a day coming that is so severe the Bible often refers to it simply as “that day.” It is so expected and so known, no other descriptors are necessary. “It will be a day of death and judgment,” as Matthew Henry says, “an awful day.” In the verse above, Paul is remembering the good work of Onesiphorus and blesses him by saying, “may he find mercy on that day.” On that day, the only way anyone will stand if we receive mercy because it is a day of justice and we are all guilty. We have all fallen short of the glory of God, and the wages of sin is death. On that day, the best Christians, even the apostles and prophets themselves, will need mercy.