"Christians"...it is an apt title for those belonging to Christ since they've accepted Christ as the Messiah and personal savior. Furthermore, they are marked in him with a seal, the Holy Spirit (cf. Ephesians 1:13). In essence, they are Spirit-filled believers sealed unto the day of redemption (cf. Ephesians 4:30).
Well, today's prosperity preachers will often say that God commanded Christians to tithe, and they will use Malachi 3:8-10 in the Old Testament times as proof.
In Joel 2:28-32, the Hebrew prophet spoke of the day of Pentecost as the beginning of Christianity. And on the day of Pentecost, Peter and others received the Holy Spirit (cf. Acts 2:1-4). Then Peter relayed the same message of the Hebrew prophet to the crowd in Acts 2:17-21. In other words, there were no Christians in the Old Testament times. The people were godly, perhaps, but not Christians. There could be no Christians before Christ died on the cross, so the Israelites in Malachi 3:8-10 were not Christians. Hence, God did not command Christians to tithe.