It also takes correct application of Scripture.
When the writer of Hebrews said, "For he who has entered His rest has himself also ceased from his works as God did from His" (Heb 4:10), he followed it up with this:
11 Let us therefore be diligent to enter that rest, lest anyone fall according to the same example of disobedience. 12 For the word of God is living and powerful, and sharper than any two-edged sword, piercing even to the division of soul and spirit, and of joints and marrow, and is a discerner of the thoughts and intents of the heart. 13 And there is no creature hidden from His sight, but all things are naked and open to the eyes of Him to whom we must give account. (Heb 4:11–13)
God can see everything going on inside a person's heart. Nothing is hidden from His sight. He knows when a person has rested from his own works and has put all his hope in Christ. And He knows when they have not done so. Since we must all give account of ourselves to Him, and since He sees everything going on inside our hearts, we each must be dilligent to enter His rest through ceasing from our own works and fully trusting in Christ for the salvation of our souls. This is what it means to believe in Jesus.