"Whereof the Holy Ghost also is a witness to us: for after that He had said before" Heb 10:15
"The Spirit itself beareth witness with our spirit, that we are the children of God" Rom 8:16
"He that believeth on the Son of God hath the Witness in himself: he that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son." 1 John 5:10

Witness of the Holy Spirit
- to us (Heb 10:15)
- with us (Rom 8:16)
- in us (1 John 5:10)

Full confirmation of the Holy Spirit in the experience of believers.