Romans 8:16

The same spirit certifieth our spirit that we are the sons of God.

2 Corinthians 1:22

which hath also sealed us, and hath given the earnest of the spirit into our hearts.

2 Corinthians 5:5

He that hath ordained us for this thing, is God: which very same hath given unto us the earnest of the spirit.

Ephesians 1:13

In whom also ye - after that ye heard the word of truth, I mean the gospel of your salvation wherein ye believed - were sealed with the holy spirit of promise,

2 Corinthians 1:12

Our rejoicing is this: the testimony of our conscience, that in singleness of heart and with godly pureness - and not in fleshly wisdom, but by the grace of God - we have had our conversation in the world, and most of all to you-wards.

Ephesians 4:30

And grieve not the holy spirit of God, by whom ye are sealed unto the day of redemption.

1 John 3:19-22

for thereby we know that we be of the truth, and so shall we certify our hearts in his sight.

1 John 4:13

Hereby know we, that we abide in him, and he in us: For he hath given us of his spirit.

1 John 5:10

He that believeth in the son of God hath the witness in himself. He that believeth not God, maketh him a liar, because he doth not believe the witness that God hath testified of his son.

Romans 8:23

Not they only, but even we also: which have the first fruits of the spirit mourn in ourselves and wait for the adoption and look for the deliverance of our bodies.

Romans 8:26

Likewise, the spirit also helpeth our infirmities. For we know not, what to desire as we ought: but the spirit maketh intercession mightily for us with groanings which cannot be expressed with tongue.

Treasury of Scripture Knowledge

Summary

The Spirit itself beareth witness with our spirit, that we are the children of God:

General references

Bible References

Spirit

Romans 8:23
Not they only, but even we also: which have the first fruits of the spirit mourn in ourselves and wait for the adoption and look for the deliverance of our bodies.
2 Corinthians 1:22
which hath also sealed us, and hath given the earnest of the spirit into our hearts.
2 Corinthians 5:5
He that hath ordained us for this thing, is God: which very same hath given unto us the earnest of the spirit.
Ephesians 1:13
In whom also ye - after that ye heard the word of truth, I mean the gospel of your salvation wherein ye believed - were sealed with the holy spirit of promise,
Ephesians 4:30
And grieve not the holy spirit of God, by whom ye are sealed unto the day of redemption.
1 John 4:13
Hereby know we, that we abide in him, and he in us: For he hath given us of his spirit.

With our

2 Corinthians 1:12
Our rejoicing is this: the testimony of our conscience, that in singleness of heart and with godly pureness - and not in fleshly wisdom, but by the grace of God - we have had our conversation in the world, and most of all to you-wards.
1 John 3:19
for thereby we know that we be of the truth, and so shall we certify our hearts in his sight.
1 John 5:10
He that believeth in the son of God hath the witness in himself. He that believeth not God, maketh him a liar, because he doth not believe the witness that God hath testified of his son.

General references

Galatians 3:26
For ye are all the sons of God, by the faith which is in Christ Jesus.