Romans 8:14-17

For all who are being led by the Spirit of God, these are sons of God. For you have not received a spirit of slavery leading to fear again, but you have received a spirit of adoption as sons by which we cry out, Abba! Father! The Spirit Himself bears witness with our spirit that we are children of God, and if children, heirs also, heirs of God and fellow heirs with Christ, if indeed we suffer with Him in order that we may also be glorified with Him.

Galatians 4:4-6

But when the fullness of the time came, God sent forth His Son, born of a woman, born under the Law, In order that He might redeem those who were under the Law, that we might receive the adoption as sons. And because you are sons, God has sent forth the Spirit of His Son into our hearts, crying, 'Abba! Father'!

Hebrews 12:8

But if you are without discipline, of which all have become partakers, then you are illegitimate children and not sons.