Witness of the Holy Spirit: Given to Saints: On Believing
Source: TTT
Acts 15:8
And God, who knows the heart, showed His approval by giving the Holy Spirit to them, just as He did to us.
1 John 5:10
Whoever believes in the Son of God has this testimony within him; whoever does not believe God has made Him out to be a liar, because he has not believed in the testimony that God has given about His Son.