believe the gospel

John 1:12

But as many as received Him, to them He gave the right to become children of God, to those who believe in His name:

John 20:31

but these are written that you may believe that Jesus is the Christ, the Son of God, and that believing you may have life in His name.

Romans 10:9-13

9 that if you confess with your mouth the Lord Jesus and believe in your heart that God has raised Him from the dead, you will be saved. 10 For with the heart one believes unto righteousness, and with the mouth confession is made unto salvation. 11 For the Scripture says, "Whoever believes on Him will not be put to shame." 12 For there is no distinction between Jew and Greek, for the same Lord over all is rich to all who call upon Him. 13 For "whoever calls on the name of the LORD shall be saved."

1 Cor 1:21, 23, 30

21 For since, in the wisdom of God, the world through wisdom did not know God, it pleased God through the foolishness of the message preached to save those who believe. . . . . 23 but we preach Christ crucified, to the Jews a stumbling block and to the Greeks foolishness, . . . .30 But of Him you are in Christ Jesus, who became for us wisdom from God--and righteousness and sanctification and redemption--