"This is My beloved Son, with whom I am well-pleased; listen to Him!" (Matthew 17:5)
"If you love Me, you will keep My commandments." (John 14:15)
"Do not think that I came to abolish the Law or the Prophets; I did not come to abolish but to satisfy." (Matthew 5:17)
"It is finished!" (John 19:30)
That is testimony of Jesus Christ, words and actions (action at the cross), the witness of Lord Jesus. Since Jesus said "It is finished!" then anyone who says otherwise or teaches otherwise contradicts the Word of God such as He is come to satisfy the Law.
Concerning Revelation 14:12, we find "keep the commandments of God, and the faith of Jesus". Faith and belief are synonyms. Again, "commandments of God" as well as "the faith of Jesus" are:
"the government will rest on His shoulders" (Isaiah 9:6)
"whoever causes one of these little ones who believe in Me to stumble, it would be better for him to have a heavy millstone hung around his neck, and to be drowned in the depth of the sea. Woe to the world because of [its] stumbling blocks! For it is inevitable that stumbling blocks come; but woe to that man through whom the stumbling block comes!" (Matthew 18:6-7)
"Truly, truly, I say to you, unless one is born again he cannot see the kingdom of God." (John 3:3)
"Truly, truly, I say to you, unless one is born of water and the Spirit he cannot enter into the kingdom of God. That which is born of the flesh is flesh, and that which is born of the Spirit is spirit. Do not be amazed that I said to you, 'You must be born again.' The wind blows where it wishes and you hear the sound of it, but do not know where it comes from and where it is going; so is everyone who is born of the Spirit." (John 3:5-8)
"Truly, truly, I say to you, he who hears My word, and believes Him who sent Me, has eternal life, and does not come into judgment, but has passed out of death into life." (John 5:24)
"For if you believed Moses, you would believe Me, for he wrote about Me. But if you do not believe his writings, how will you believe My words?" (John 5:26-27)
Powerful Word! Moses said:
"The LORD your God will raise up for you a prophet like me from among you, from your countrymen, you shall listen to him. This is according to all that you asked of the LORD your God in Horeb on the day of the assembly, saying, 'Let me not hear again the voice of the LORD my God, let me not see this great fire anymore, or I will die.' The LORD said to me, 'They have spoken well. I will raise up a prophet from among their countrymen like you, and I will put My words in his mouth, and he shall speak to them all that I command him. It shall come about that whoever will not listen to My words which he shall speak in My name, I Myself will require [it] of him." (Deuteronomy 18:15-19)
In 1 John 2:3-4, the "His commandments" are "Jesus Christ the righteous' commandments" because 1 John 2:1 identifies Him, here is verse 1: "My little children, I am writing these things to you so that you may not sin. And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous".