'Confirms' in the Bible

The Spirit himself confirms to our spirit that we are children of God,

I am telling the truth because I belong to the Messiah I am not lying, and my conscience confirms it by means of the Holy Spirit.

For with the heart a person believes [in Christ as Savior] resulting in his justification [that is, being made righteous—being freed of the guilt of sin and made acceptable to God]; and with the mouth he acknowledges and confesses [his faith openly], resulting in and confirming [his] salvation.