The Father does all things in the Name of His Son. His promise of forgiveness is entirely predicated upon repentance with first a belief in His Only Begotten Son. Through Him, and Him alone, "will I have mercy upon you." This is an integral part of the Plan of Redemption. Whatsoever ye do, do it in My Name, was the commandment of Jesus. (III Nephi 27:7)
All them that repent, having a sincere heart and a steadfast spirit, can claim and will receive mercy through Mine Only Begotten Son, and will find rest with Me in My Kingdom, thus saith the Lord who is God over all the Earth.