Why is it a greater sin to not forgive than to wrong someone?

The Lord has taught: “Ye ought to forgive one another; for he that forgiveth not his brother his trespasses standeth condemned before the Lord; for there remaineth in him the greater sin.

“I, the Lord, will forgive whom I will forgive, but of you it is required to forgive all men” (D&C 64:9–10).

When we withhold our forgiveness, we are placing our limited judgment above the Lord’s perfect judgment. He has a perfect view of people’s hearts and circumstances, and judgment belongs to Him alone. He will ultimately deal out perfect justice and perfect mercy to all—both those who wrong others and those who are wronged.

In addition, by requiring us to forgive, the Lord is helping us to choose happiness over misery, to abandon our bitter grudges and resentments and receive healing through His grace. Then we discover that, as Elder Kevin R. Duncan of the Seventy has reminded us, “The Savior’s Atonement is not just for those who need to repent; it is also for those who need to forgive” (Apr. 2016 general conference).