Romans 8:14–16

The Spirit testifies that we are God's children and leads us to cry “Abba, Father”

14For all who are led by the Spirit of God, these are sons of God.

15For you did not receive a spirit of slavery leading again to fear, but you received a spirit of adoption as sons, by which we cry out, Abba, Father.

16The Spirit himself testifies with our spirit that we are children of God,

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In its context

12So then, brothers, we are debtors, not to the flesh, to live according to the flesh.

13For if you live according to the flesh, you are going to die; but if by the Spirit you put to death the deeds of the body, you will live.

…

17and if children, also heirs: heirs of God and fellow heirs of the Messiah, if indeed we suffer with him so that we may also be glorified with him.

18For I consider that the sufferings of the present time are not worthy to be compared with the glory that is going to be revealed to us.

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Its words in the original

The Holy Spirit