I disagree with this take entirely. This is not a promise from Jesus but an imperative. This comes from the Sermon on the Mount which is Jesus sermon on what the "law" really demands. He is telling that if you wish to be saved by adherence to the law then you must keep it perfectly, just as the Father keeps it. He makes the same point later in the sermon when he says, "For I say unto you, that except your righteousness shall exceed the the righteousness of the scribes and Pharisees, ye shall in no case enter into the Kingdom of Heaven." The Scribes and Pharisees keep the law better than anyone and even that wasn't good enough - perfection is required if that is to save you. The Sermon on the Mount shows us that salvation by obedience to God's law requires a level of righteousness that no human can live up to. It shows us why we need a Savior.
Amen. The Sermon on the Mount not only condemns our actions but what is in our hearts and minds (thoughts). We are all guilty as charged. Praise our Lord and Savior Jesus Christ for His spotless cloak of Righteousness.