Colossians 1:14 In whom we have redemption through his blood, even the forgiveness of sins:
Psalm 130:4 But there is forgiveness with thee, that thou mayest be feared.
Daniel 9:9 To the Lord our God belong mercies and forgivenesses, though we have rebelled against him;
Ephesians 1:7 In whom we have redemption through his blood, the forgiveness of sins, according to the riches of his grace;
Luke 7:47 Wherefore I say unto thee, Her sins, which are many, are forgiven; for she loved much: but to whom little is forgiven, the same loveth little.
Ephesians 4:32 And be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ’s sake hath forgiven you.
1 John 2:12 I write unto you, little children, because your sins are forgiven you for his name’s sake.
I could fill a whole book on biblical promises just on forgiveness. If I did two major points might be lost in all those verses. One, God only forgives because of what Jesus Christ did on the Cross. Nothing we have ever done or will do can ever replace or improve on that work. We owe all that to Christ. Two, without forgiveness we all would be stuck in one of two places pride or depression. Neither of those two conditions put us in a place to serve the will of God.
So service seems like the next promise to address. Yes, service is a promise.