Jesus ends His Sermon on the Mount speaking with authority and advising those who hear Him to build their lives on His words, the everlasting rock, rather than entirely on the wisdom of the world apart from the wisdom of God.
For His last words to the disciples before being arrested, in John 14-16, Jesus says that if they love Him, they are abiding in His words. They should stay connected to Him through their faith in Him and His words if they expect to do much good in the world. Those who do not abide are separated from Him. Yet, it is the Holy Spirit and the love He instills in us that enables us to abide.
Bottom line, trusting in His death to wipe away our sins, and thus the guilt they bring, but not trusting in His words, is not salvation! Faith is trusting in all of Christ, not just part of Him. His death cleared our debt, but His resurrection showed that His words are true and trustworthy! We are saved to bring God glory and that is not being done if we ignore His word and only trust in a one time vain confession.
Some think following His words is a works based salvation, that we might boast, but rather it is the sign that shows we know Him and are saved. 1 Jn 2:3-6: 3 And by this we know that we have come to know him, if we keep his commandments. 4 Whoever says “I know him” but does not keep his commandments is a liar, and the truth is not in him, 5 but whoever keeps his word, in him truly the love of God is perfected. By this we may know that we are in him: 6 whoever says he abides in him ought to walk in the same way in which he walked.
Matthew 7:24-29; John 14:15-26