Romans 8:12-21
Thus we are no longer "debtors to the flesh", this greedy and cruel creditor (v. 12). We have become children of God, and our Father does not want us to be in bondage. He Himself has paid all that we owed so that we might be free, dependent on Him alone. In old times the Roman slave could be set free, and in exceptional cases be adopted by his master with all the rights of inheritance. This is a feeble picture of what God has done for His poor fallen creatures, sin-stained and rebels against Him. He has not only granted them forgiveness, justification and complete deliverance, but has made them members of His own family. And they are sealed by His Spirit, by whom also the children know their relationship with the Father. "Dada" (Abba in Hebrew) is often the first distinct word that a little child says (vv. 15, 16; John 2:13 end).
In addition to this assurance which He gives us, the Spirit teaches us how to put to death (that is not to let them manifest themselves) the deeds of the flesh (v. 13). It is by allowing ourselves to be led by the Spirit that we shall realise that we are sons of God (v. 14; cf. Matthew 5:44-45) while waiting to be manifested as such to all creation (v. 19).