Nowhere does the Bible say that, but rather it states the opposite. In Romans 10:5-8, Paul referred to Deuteronomy 30 as the word of faith that we proclaim in regard to the righteousness that is by faith proclaiming that the Law of God is not too difficult for us to obey and that obedience to it brings life and a blessing while disobedience brings death and a curse, so choose life! Moreover, there are many example of people in the Bible who did keep the law, such as with those in Joshua 22:1-3, Luke 1:5-6, Revelation 14:12, and Revelation 22:14.
If we needed to have perfect obedience to the law, then repentance would have no value, so the fact that repentance has value democrats that we are not required to have perfect obedience. The only reason why someone would need to have perfect obedience to the Law of God would if they are going to give themselves to pay for the sins of the world - the rest of us can thankfully have our sins forgiven. The Law of God was never given as something that was to be obeyed apart from Christ.
Christ lived in obedience to the Law of God, so that is also the way that we live when we he is living in us, which includes keeping the 7th day holy. In Matthew 11:28-30, Jesus was inviting people to come to him for rest and to learn from him, not inviting people to come to him for rest instead of learning from his example. By Jesus saying that we would find rest for our souls he was referencing Jeremiah 6:16-19, where the Law of God is described as the good way where we will find rest for our souls. We have find rest for our souls instead of following God's instructions for how to find rest for our souls. In Revelation 14:12, those who kept faith in Christ are the same as those who kept God's commandments, so we can't have faith n Christ instead of keeping God's commandments. God is trustworthy therefore His law is also trustworthy (Psalms 19:7), so the way to trust in God for our salvation is by obediently trusting in His law and it would be contradictory to think that we should trust in God for salvation instead of trusting in His instructions. God has not given any instructions for man for how to do works of our own to contribute to our own salvation, but rather God graciously teaching us to be a doer of His law is how He is giving us His gift of salvation. Works that we do on our own would be works that are completely independent of anything that God has instructed.
The New Covenant still involves following God's law (Jeremiah 31:33, Ezekiel 36:26-27), so I'm not mixing the covenants. The Bible repeatedly connects our works with our faith such as with the examples of faith in Hebrews 11 or with James 2:18 saying that he would show his faith through his works. In Psalm 119:29-30, he wanted to put false ways far from him, for God to be gracious to him by teaching him to obey His law, and he chose the way of faith by setting it before him, so this has always been the one and only way of salvation by grace through faith, and it would be absurd to think that he wanted God to be gracious to him by teaching him how to fall from grace.