The collection of Luther’s letters, translated and edited by Theodore Tappert, give us the on-the-ground look into the great Reformer’s theological convictions. He was a Christ-exalting pastor. In counsel to the sick and dying, he stood on 2 Corinthians 12:9.
On December 30, 1534 Luther wrote to Urban Rhegius who was ill:
I believe that this trial comes to you, as it does to other brethren who occupy high stations, in order that we may be humbled. Therefore, be of good courage, let your heart be comforted, and wait on the Lord, who said to Saint Paul, “My strength is made perfect in weakness.” God is faithful. By him we were called. he will perform a good work in us until the day of Jesus Christ. Amen. This Lord have I heard, and by him have I been comforted as much as the Lord has given it to me to be.
Luther: Letters of Spiritual Counsel, 41.