The Spirit Himself bears witness with our spirit that we are children of God.
What then shall we say to these things? If God is for us, who can be against us? He who did not spare His own Son, but delivered Him up for us all, how shall He not with Him also freely give us all things? Who shall bring a charge against God's elect? It is God who justifies. Who is he who condemns? It is Christ who died, and furthermore is also risen, who is even at the right hand of God, who also makes intercession for us. Romans 8:16, 31-34
What then shall we say to these things? If God is for us, who can be against us? He who did not spare His own Son, but delivered Him up for us all, how shall He not with Him also freely give us all things? Who shall bring a charge against God's elect? It is God who justifies. Who is he who condemns? It is Christ who died, and furthermore is also risen, who is even at the right hand of God, who also makes intercession for us. Romans 8:16, 31-34