The apostles thought the return of Jesus Christ would happen within their lifetimes because they did not fully understand God's timeframe. Undoubtedly, people were becoming discouraged because they felt that matters were going awry in their world. They were frightened, anxious, and in pain, crying out, "How long, O Lord?" They were becoming impatient, and it seemed that everything was continuing as it had, and nothing was changing except for the worse. Some were becoming so discouraged that they were leaving the church.
So Peter writes that the Lord is not slack concerning His promise. God does not lie; He will send His Son to this earth. However, He is being very patient, and this is Peter's emphasis.
What kind of a plan could God devise that would produce the best in terms of character and the most in terms of the number of children who inherit His Kingdom? How could He be merciful and forgiving without being merely indulgent? What could He use as points of reference that would motivate people to continue to strive toward the conclusion of His purpose once He had mercifully forgiven them?
"That with the Lord one day is as a thousand years, and a thousand years as one day" indicates that God does not look at time as we do. To us, time is very pressing because we realize we will live only about seventy years. As we get older, the fact of death becomes an increasingly clearer reality. When we are twenty, we hardly ever think about death unless somebody close dies. But as we age, we think about death more frequently. Our bodies start running down. We do not have the vigor, energy, vitality, or strength we used to have. We are aware of these things because we begin to feel them slip away. It becomes easier for us to become impatient because we have so many things we want to do and accomplish, yet time keeps flying by.
With God, though, time is not so critical. If a thousand years with God is as a day, how much is seventy years, the life of a human being? Nothing more than the blink of an eye. How many blinks of an eye—human lifetimes—end every day? Tens of thousands of them! Blink—they are gone, but they experienced every second of their lives. They were born and played through childhood. They went to school. They became adult men and women. They married and raised families. They watched their children grow up. They fought wars. They endured droughts and famines, diseases, and depressions. They watched death approaching, and they died. All this—a blink of an eye to God.
We cannot begin to grasp the enormity of what God is doing until we begin to consider the scope of the thousands of years that have already passed and the billions of lives that have been lived. We must begin to look at the much bigger picture yet retain a human perspective of time and life, understanding that, to God, time means almost nothing because He has power over life and death. Vast and awesome is the scope of what God is working out, but we need to look at what is going on through the understanding God has given us of Himself.