There are two sets of commandments in the New Testament. One set of commandments is in the law and the other set of commandments, are the commandments that Jesus gave.
1 John 2:4
The one who says, “I have come to know Him,” and does not keep His commandments, is a liar, and the truth is not in him;
1 John 3:23-24
This is His commandment, that we believe in the name of His Son Jesus Christ, and love one another, just as He commanded us. The one who keeps His commandments abides in Him, and He in him.
1 John 4:21
And this commandment we have from Him, that the one who loves God should love his brother also.
1 John 5:2
By this we know that we love the children of God, when we love God and observe His commandments.
John 13:34
A new commandment I give to you, that you love one another, even as I have loved you, that you also love one another.
Do you agree that Jesus set a sinless example of how to walk in obedience to the Mosaic Law?
Do you agree that Jesus did not hypocritically preach something other than what he practiced?
If so, then you should agree that Jesus taught obedience to the Mosaic Law both by word and by example. God is not in disagreement with Himself about which laws we should follow, so the Law of Christ is the same as the Law of the Spirit and the Law of the Father, which was given to Moses. In John 14:24, Jesus said that his teachings were not his own, but that of the Father, so he did not give his own set of commandments. In Deuteronomy 4:2, it is a sin to add to or subtract from the law, so if Jesus had taught his own set of commandments, then he would have sinned and disqualified himself from being our Savior. In 1 John 2:3-6, it associates the instruction to follow Christ's commandments with the instruction that those who are in Christ are obligated to walk in the same way he walked, so again what Jesus taught by word was the same as what he taught by example, and as his followers we are told to follow his example (1 Peter 2:21-22).
To believe in the one who he has sent is to believe in who he is, what he was sent to accomplish, and in what that means for how we should live our lives. The Bible often uses the same terms to describe the nature of God as it does to describe the nature of God's law, which is because it is His instructions for how to express His nature, such as with it being holy, righteous, and good (
Romans 7:12), or with justice, mercy, and faithfulness being weightier matters of the law (
Matthew 23:23). God's ways reveal His nature and there are many verses that describe the Mosaic Law as being instructions for how to walk in God's ways, such as
Deuteronomy 10:12-13,
Isaiah 2:2-3,
Joshua 22:5,
Psalms 103:7, and many others. Jesus is the radiance of God's glory and the exact expression of His nature (
Hebrews 1:3), which looked like life lived in sinless obedience to the Mosaic Law. The Mosaic Law reveals God's ways or is the way (
Jeremiah 6:16-19), the truth (
Psalms 119:142), and the life (
Deuteronomy 32:47), so Jesus is the personification of God's nature, he is the Word of God made flesh, and he put the nature of the Father on display, which is why he is the personification of the way, the truth, and the life, that no one comes to the Father but through him, and that anyone who has seen him as seen the Father (
John 14:6-9). In
John 5:39-40, Jesus said that the Scriptures testify about him, so the whole goal of the Mosaic Law is to teach us about how to know or have a relationship with Christ and about how to testifying about who he is, which is why he is the goal of the law (
Romans 10:4). In
John 6:40, Jesus said that everyone who looks on the Son and believes in him should have eternal life, in
Matthew 19:17, Jesus said that if we want enter into eternal life, then obey the commandments, and in
Revelation 14:12, those who kept faith in Jesus are the same as those who kept God's commandments, so I think that obedience to the Mosaic Law is what it looks like to believe in who Jesus is.
Jesus began his ministry calling people to repent for the Kingdom of God is at hand (
Matthew 4:17-23), and the Mosaic Law is how his people knew what sin is, so repenting from our disobedience to it is an integral part of the Gospel message, which he prophesied would be proclaimed to all nations (
Matthew 24:12-14). He also said in those verses that because of lawlessness the love of many will grow cold, but those who endure to the end will be saved. In
Psalms 119:29, David wanted God to be gracious to him by teaching him to obey His law, and in
Titus 2:11-14, our salvation is described as being trained by grace to do what is godly, righteous, and good, and to renounce doing what is ungodly, which is what the Mosaic Law was given to instruct how to do, so God graciously teaching us how to live in obedience to His law is itself part of the content of His free gift of salvation from sin, and sin is living in transgression of God's law (
1 John 3:4). Furthermore,
Titus 2:14 says that Jesus gave himself to redeem us from all lawlessness and to purify for himself a people of his own possession who are zealous for doing good works, so if we believe both in what Jesus was sent to accomplish through his ministry and through his death on the cross and understand what that means for how we should live our lives, then we will express that belief through repenting and becoming zealous for doing good works in obedience to the Mosaic Law (Acts 21:20).
In Matthew 22:36-40, Jesus summarized the Mosaic Law as being about how to love God and our neighbor, so that is how he expressed his love and how we are to love as he loved. Over and over, the both the OT and the NT associate love with obedience to God's commandments: