A good man. The predominant idea in ἀγαθός is simply "goodness," moral excellence. So in Matthew 19:16, "Good Master." To which our Lord answers, "There is none good but One." In Luke 23:50 Joseph of Arimathaea is ἀνὴρ ἀγαθὸς καὶ δίκαιος, "a good man and a righteous."
In Matthew 5:45 πονηροὶ καὶ ἀγαθοί, "the evil and the good," are contrasted. In classical Greek the common phrase, καλὸς κἀγαθός, describes an honorable and good man. It is pleasing to read this testimony from Luke, Paul's companion and friend, Full of the Holy Ghost and of faith.
So Stephen is described (Acts 6:5) as "full of faith and of the Holy Spirit." The Holy Spirit is spoken of in both places as a Spirit of power and demonstration in preaching the Word. No reason is apparent why the R.
T., having altered Ghost to Spirit in Acts 6:5, retains Ghost here. Much people, etc.; the direct consequence of the energy of the Holy Ghost in Barnabas's ministry.