The Spirit Himself bears witness with our spirit that we are children of God. (Romans 8:16)
Let me point out one simple, historic fact—a conclusion at which most sound Bible scholars have arrived. There is a direct correspondence in time periods between the deliverance of Israel out of Egypt and the experience of the early Christians.
The Passover lamb’s execution corresponds to the day on which Jesus died.
The crossing of the Red Sea corresponds to Jesus’ resurrection from the grave.
The receiving of the Law at Mount Sinai, fifty days after the Passover, corresponds to the outpouring of the Spirit at Pentecost.
I point this out because when you have been delivered through the blood and through the resurrection of Jesus, you have two choices: you can go to Sinai, or you can go to Pentecost. Quite a lot of people go to Sinai—they go back under the law. They “receive the spirit of bondage again to fear” (verse 15). But Paul said, in essence, “You have not received a spirit of bondage to fear; you have received the Spirit of adoption, who tells you that you are a child of God.”