In the following Scriptures we see the O.T. Gospel. Jesus was preached in the O.T. and the Apostles used those Scriptures to preach in the N.T.
When they had appointed a day for him, they came to him at his lodging in greater numbers. From morning till evening he expounded to them, testifying to the kingdom of God and trying to convince them about Jesus both from the Law of Moses and from the Prophets. (Acts 28:23 ESV)
Think about this Scripture in 28:23. There were no written New Testaments for the Preachers to carry around. Paul was explaining our Lord Jesus Christ and the Kingdom of God from Old Testament Scriptures. Yet today, we have Pastors who would say it is not necessary to study the OT because it has been done away with. Really? Paul was using the Law of Moses, the first 5 Books of the OT and the Prophets, the rest of the OT to explain the birth, life, death, resurrection, and current role of our Lord Jesus Christ. Incredible. The OT is the shadow and the NT is the substance. Both are needed. In fact John and our Lord Jesus Christ said something about OT Scriptures.
When therefore he was raised from the dead, his disciples remembered that he had said this, and they believed the Scripture and the word that Jesus had spoken. (John 2:22 ESV)
What Scripture did they believe? The NT had not been written yet. They were preaching Jesus from the OT.
Whoever believes in me, as the Scripture has said, ‘Out of his heart will flow rivers of living water.’” (John 7:38 ESV)
Look at that Jn.7:38 passage. They were believing on Jesus as the OT spoke about Him.
And some were convinced by what he said, but others disbelieved. (Acts 28:24 ESV)
We have the same problem today as spoken about in 28:24. Some will believe and others will not. These are religious leaders that verse 24 is addressing. Yes, it is sad but true, put every Sunday there are pulpits all across America that are being filled with lost preachers. They have a social gospel, a cultural gospel, or a feel-good self-help gospel, all of which are not gospels.
And disagreeing among themselves, they departed after Paul had made one statement: “The Holy Spirit was right in saying to your fathers through Isaiah the prophet: (Acts 28:25 ESV)
In verse 25 we see then what we see today, the Word gets preached and people make up their own mind with their own opinions about the Word of God. It is so easy to say in ignorance, "I disagree."
“‘Go to this people, and say, “You will indeed hear but never understand, and you will indeed see but never perceive.” (Acts 28:26 ESV)
For this people's heart has grown dull, and with their ears they can barely hear, and their eyes they have closed; lest they should see with their eyes and hear with their ears and understand with their heart and turn, and I would heal them.’ (Acts 28:27 ESV)
The problem: Seeing they do not see, hearing they do not hear.
Charles Morris. Founder and Senior Pastor of RSI Ministry, RSI School of Ministry, and RSI Publishing L.L.C..