How does believing all this benefit you?
That I am righteous in Christ before God and an heir of eternal life.
Scripture references
How are you righteous before God?
Only through true faith in Jesus Christ. My conscience accuses me that I have grievously broken all God’s commandments and kept none of them, and that I am still inclined to all evil.
Nevertheless, without any merit of mine and solely by grace, God grants and credits to me the perfect satisfaction, righteousness, and holiness of Christ. He does so as if I had never had or committed any sin, and as if I had fulfilled all the obedience that Christ has fulfilled for me, provided that I receive this benefit with a believing heart.
Why do you say that you are righteous by faith only?
Not that I am acceptable to God on account of the worthiness of my faith, but because only the satisfaction, righteousness, and holiness of Christ is my righteousness before God, and that I cannot receive and apply the same to myself any other way than by faith only.