He might mention the scripture in Leviticus 5 which will let other Masons know that they can be released as well. A sample resignation letter is provided. You may print it with your browser. Writing such a letter can result in a major step on the road to spiritual healing. The letter should be written to the members of the Lodge.
Masonic regulations require that it be read to the membership.
Sometimes this happens. It is a great witness. It provides a sense of closure for the man. If he writes such a letter, it is doubtful that he will ever be tempted to return to the Lodge. If the pastor is a Godly man, it would also be good for the repentant Mason to privately tell the pastor that he has renounced Freemasonry.