Romans 8:16

For the same Spirit bears witness unto our spirit that we are sons of God,

2 Corinthians 1:22

who has also sealed us and given the earnest of the Spirit in our hearts.

2 Corinthians 5:5

Now he that has made us for this same thing is God, who has likewise given unto us the earnest of the Spirit.

Ephesians 1:13

In whom ye also trusted, hearing the word of truth, the gospel of your saving health; in whom also after ye believed, ye were sealed with that Holy Spirit of the promise,

2 Corinthians 1:12

For our rejoicing is this, the testimony of our conscience, that in simplicity and godly sincerity, not with carnal wisdom, but by the grace of God, we have had our conversation in the world and more abundantly towards you.

Ephesians 4:30

And do not grieve the Holy Spirit of God with which ye are sealed for the day of redemption.

1 John 3:19-22

And in this we know that we are of the truth and have our hearts certified before him.

1 John 4:13

In this we know that we abide in him, and he in us, in that he has given us of his Spirit.

1 John 5:10

He that believes in the Son of God has the witness of God in himself; he that does not believe God has made God a liar; because he does not believe the witness that God has testified of his Son.

Romans 8:23

And not only they, but ourselves also who have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption, that is to say, the redemption of our body.

Romans 8:26

And likewise also the Spirit helps our weakness; for we know not how to pray as we ought, but the Spirit itself makes entreaty for us with groanings which cannot be uttered.

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
And not only they, but ourselves also who have the firstfruits of the Spirit, even we ourselves groan within ourselves, waiting for the adoption, that is to say, the redemption of our body.
2 Corinthians 1:22
who has also sealed us and given the earnest of the Spirit in our hearts.
2 Corinthians 5:5
Now he that has made us for this same thing is God, who has likewise given unto us the earnest of the Spirit.
Ephesians 1:13
In whom ye also trusted, hearing the word of truth, the gospel of your saving health; in whom also after ye believed, ye were sealed with that Holy Spirit of the promise,
Ephesians 4:30
And do not grieve the Holy Spirit of God with which ye are sealed for the day of redemption.
1 John 4:13
In this we know that we abide in him, and he in us, in that he has given us of his Spirit.

With our

2 Corinthians 1:12
For our rejoicing is this, the testimony of our conscience, that in simplicity and godly sincerity, not with carnal wisdom, but by the grace of God, we have had our conversation in the world and more abundantly towards you.
1 John 3:19
And in this we know that we are of the truth and have our hearts certified before him.
1 John 5:10
He that believes in the Son of God has the witness of God in himself; he that does not believe God has made God a liar; because he does not believe the witness that God has testified of his Son.

General references

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