Third Answer — a practical one: Make good use of what to you seems to be delay.
The Lord is not slack. — We are in doubt whether “the Lord” means Christ or God the Father. In 2 Peter 3:8 “the Lord” certainly means God; and this is in favour of the same meaning here. On the other hand, “concerning His promise” naturally refers to Christ’s promise that He will return. The same doubt recurs with regard to 2 Peter 3:15 (see Note there). By “is not slack is meant “does not delay beyond the time appointed.” There is no dilatoriness; He waits, but is never slow, is never late.
Concerning his promise. — The Greek construction is peculiar, formed on the analogy of a comparative adjective — “is not slower than his promise.” (Comp. Romans 3:23.)
But is longsuffering. — (Comp. 2 Peter 3:15 and 1 Peter 3:20. As St. Augustine puts it, God is patiens quia aeternus — longsuffering because He is eternal. He who is from everlasting to everlasting can afford to wait. (Comp. the Shepherd, Sim. VIII. xi. 1.)
To us-ward. — The true reading, beyond all doubt, is towards you. It is specially natural here that St. Peter should not include himself among those whom he addresses; for he is writing mainly to Gentile Christians (2 Peter 1:1), and this longsuffering of God had been conspicuous in His dealings with the Gentiles (Romans 11:11-36.) (See second Note on 1 Peter 1:12.)