How do we know if someone is speaking by the Holy Spirit?

The distinguishing mark of a speaker guided by the Holy Spirit is their focus on glorifying the Lord Jesus Christ and testifying to His work. As mentioned in John 15:26, the Spirit, sent by Christ, is designated to bear witness of Him. If a teacher or preacher directs attention to the flesh, human efforts, or emphasizes what individuals must do to earn favor with God, they are not operating under the true Spirit of Christ. True spiritual teaching leads believers to rest in the completed work of Christ rather than their own abilities or efforts, and it affirms the sufficiency of Christ in salvation.