The times of ignorance God overlooked, but now he commands all people everywhere to repent, because he has fixed a day on which he will judge the world in righteousness by a man whom he has appointed; and of this he has given assurance to all by raising him from the dead." Acts 17:30-31

Therefore, as the Holy Spirit says, "Today, if you hear his voice, do not harden your hearts as in the rebellion, on the day of testing in the wilderness, where your fathers put me to the test and saw my works for forty years. Therefore I was provoked with that generation, and said, 'They always go astray in their heart; they have not known my ways.' As I swore in my wrath, 'They shall not enter my rest.'" Take care, brothers, lest there be in any of you an evil, unbelieving heart, leading you to fall away from the living God. But exhort one another every day, as long as it is called "today," that none of you may be hardened by the deceitfulness of sin. For we have come to share in Christ, if indeed we hold our original confidence firm to the end. As it is said, "Today, if you hear his voice, do not harden your hearts as in the rebellion." Hebrews 3:7-15

Since therefore it remains for some to enter it, and those who formerly received the good news failed to enter because of disobedience, again he appoints a certain day, "Today," saying through David so long afterward, in the words already quoted, "Today, if you hear his voice, do not harden your hearts." Hebrews 4:6-7