Both John Whitmer and his brother Peter asked God many times what they could do which would be of the greatest worth. His response to both of them was the same:
The thing which will be of the most worth unto you will be to declare repentance unto this people, that you may bring souls unto me, that you may rest with them in the kingdom of my Father.Doctrine and Covenants 15:6, 16:6
The prophet Alma recognized this truth. After resigning from his role as chief judge to dedicate himself exclusively to the ministry (Alma 4:15-20), after preaching the gospel in many cities and seeing a dramatic change in people like Amulek and Zeezrom (Alma 10:1-11, Alma 15:3-12), and after seeing the miraculous results of the missionary service of his friends, the sons of Mosiah (Alma 17:1-4), he expressed his deepest desire in these poetic words:
O that I were an angel, and could have the wish of mine heart, that I might go forth and speak with the trump of God, with a voice to shake the earth, and cry repentance unto every people!
Yea, I would declare unto every soul, as with the voice of thunder, repentance and the plan of redemption, that they should repent and come unto our God, that there might not be more sorrow upon all the face of the earth.Alma 29:1-2
Alma tempered his enthusiasm by reminding himself to act within the constraints he had been given, but this desire to declare repentance was real and heartfelt. He later urged his son Corianton, “Go thy way, declare the word with truth and soberness, that thou mayest bring souls unto repentance, that the great plan of mercy may have claim upon them” (Alma 42:31).
Preach My Gospel, the handbook for missionaries, provides the following explanation in the first chapter:
As you teach people to understand the Restoration of the fulness of the gospel of Jesus Christ, you “declare repentance” (Doctrine and Covenants 15:6). Repentance involves a change of heart and a desire to forsake sin and serve God. It involves humbly yielding to the Spirit and submitting to God’s will. It requires that people increase their commitment to live in agreement with God’s will. Repentance requires a sincere and lasting change of thoughts, desires, habits, and actions. It is a positive experience that brings joy and peace. Be bold and loving in helping people understand what they must do to repent. By inviting people to make commitments, you can effectively raise a voice of both warning and hope.Preach My Gospel, Chapter 1: What Is My Purpose as a Missionary?
If the purpose of this life is for us to become more like God, then we help Him fulfill that purpose by being willing to change and by helping others overcome their natural resistance to change. To “declare repentance” is to affirm, to ourselves and to others, that we can change and that personal improvement brings joy.
Today, I will “declare repentance.” I will reaffirm to myself and to others that we can improve and progress, that God will help us change in ways that are both meaningful and durable.