New Defender's Study Bible Notes
5:3 lie to the Holy Ghost. The sin of Ananias and Sapphira was not greed, for they did give a substantial gift to the church. Rather it was pride, desiring the praise of others in the church, and lying, in order to gain that prestige. Even so, it might not seem to be such a crime as to warrant immediate death. The judgment, however, came from God, not Peter, and was accomplished by providential miracle. In this very first church of our church age, it was absolutely vital that hypocrisy not gain a foothold and set a dangerous precedent. Consequently, it was expeditious in God’s eyes, for Him to enact His judgment of death on sin speedily (Romans 6:23) in this case.
5:4 unto God. In Acts 5:3, Peter said Ananias had lied to the Holy Ghost: in Acts 5:4, he said Ananias had lied to God. Thus, God and the Holy Ghost are used synonymously, showing clearly that the Holy Spirit is God.