2 Cor 6:1-2, Lk 4:17-19, Heb 3:7-8, Heb 4:7, Acts 16:31
In the Old Testament, God heard the prayer of Christ on the day of salvation to come, and made Christ the covenant of the people of Israel to save the people of Israel. (Isa 49:8)
Isa 49:8 Thus saith the Lord, In an acceptable time have I heard thee, and in a day of salvation have I helped thee: and I will preserve thee, and give thee for a covenant of the people, to establish the earth, to cause to inherit the desolate heritages;
Now is the day of salvation by believing in Jesus Christ, the time of grace. (2 Corinthians 6:1-2, Luke 4:17-19)
2 Corinthians 6:1 We then, as workers together with him, beseech you also that ye receive not the grace of God in vain. 2 (For he saith, I have heard thee in a time accepted, and in the day of salvation have I succoured thee: behold, now is the accepted time; behold, now is the day of salvation.)
Luke 4:17 And there was delivered unto him the book of the prophet Esaias. And when he had opened the book, he found the place where it was written, 18 The Spirit of the Lord is upon me, because he hath anointed me to preach the gospel to the poor; he hath sent me to heal the brokenhearted, to preach deliverance to the captives, and recovering of sight to the blind, to set at liberty them that are bruised, 19 To preach the acceptable year of the Lord.
When God reveals that Jesus is the Christ through the Old and New Testaments, we should not harden our hearts and listen to His voice. (Heb 3:7-8, Heb 4:7)
Heb 3:7 Wherefore (as the Holy Ghost saith, To day if ye will hear his voice, 8 Harden not your hearts, as in the provocation, in the day of temptation in the wilderness:
Heb 4:7 Again, he limiteth a certain day, saying in David, To day, after so long a time; as it is said, To day if ye will hear his voice, harden not your hearts.
We are saved when we believe in Jesus as the Christ. (Acts 16:31)
Acts 16:31 And they said, Believe on the Lord Jesus Christ, and thou shalt be saved, and thy house.