In the new testament, we are warned about false human teachers, but there are also deceiving spirits to avoid. Jesus warns us about false prophets and false messiahs in Matt 24:24 and Mark 13:22. Colossians 2:8-10 says to reject corrupt theology based on the philosophies of worldly spiritual teachings. 1 John 4:1-4 says to test the spirits and ignore the ones that steer people away from what Jesus and his apostles taught. Gal 1:8 warns about false gospel preached by anyone including fallen angels. 2 Cor 11:13-15 says that false teachers pretending to be godly is like how Satan pretends to be an angel of light. Also, Col 2:18 says angels shouldn’t be worshiped or prayed to.

Something I noticed is that angelic messages stopped after the Holy Spirit was distributed. In Acts 10:3-8 and the last angelic message was given to Cornelius telling him to send for Peter, so he could hear the gospel and receive the holy spirit. When Peter ministered to him, he and his family were among the first non-Jews and non-Samaritans to receive the holy spirit. After that angels still appear to help believers, like when one broke Peter out of prison in Acts 12:6-18, but they don’t give any further messages about theology. For new theology, Jesus himself would visit them or they would get revelation from the holy spirit. Paul was visited by Jesus at least 3 times in his ministry, first in Acts 9:1-19, [recalled in Acts 22:3-16 and Acts 26:9-18], then in Acts 22:17-21, and lastly in Acts 23:11. The vision that John has while in exile on Patmos, that he writes down in the Book of Revelation, is initiated with a visit from Jesus. There was an angel involved was in the vision, but that angel didn’t give John a message for the churches, he simply guided John through the vision after Jesus’s initial message. The apostle John twice mistakenly worships an angel in the book of Revelation and is scolded both times. The Angel says don’t worship me I am just a servant like you (Rev 19:10, & Rev 22:9). Remember, the hosts of heaven aren’t to be worshiped, that is idolatry.

Don’t pray to angels:
Col 2:18 (NLT) Don’t let anyone condemn you by insisting on pious self-denial or the worship of angels, saying they have had visions about these things. Their sinful minds have made them proud, 19 and they are not connected to Christ, the head of the body. For he holds the whole body together with its joints and ligaments, and it grows as God nourishes it.

Don’t follow worldly pagan-based spiritual practices:
Colossians 2:8 8 Don’t let anyone capture you with empty philosophies and high-sounding nonsense that come from human thinking and from the spiritual powers of this world, rather than from Christ. 9 For in Christ lives all the fullness of God in a human body. 10 So you also are complete through your union with Christ, who is the head over every ruler and authority

False angels:
Gal 1:8 Let God’s curse fall on anyone, including us or even an angel from heaven, who preaches a different kind of Good News than the one we preached to you.

False Teachers:
2 Cor 11:13 These people are false apostles. They are deceitful workers who disguise themselves as apostles of Christ. 14 But I am not surprised! Even Satan disguises himself as an angel of light. 15 So it is no wonder that his servants also disguise themselves as servants of righteousness. In the end they will get the punishment their wicked deeds deserve.

This would explain why angelic visitations post the first century started whole new religions like Islam (supposedly “Gabriel”) and Mormonism (Moroni). Mormon churches often have statues of Moroni on top of their churches. Ultimately, if an “angel” is coming to teach you a new gospel and an alternative theology, then you know that angel is corrupt. In this new covenant, they’re only there to help us in our deliverance from physical danger. It is the Holy Spirit who is the Advocate/Comforter (John 14:16-26), that represents God’s voice for us now (John 16:5-15), not messengers (angels).

I leave you with a word from John:
1 John 4:1 Dear friends, do not believe everyone who claims to speak by the Spirit. You must test them to see if the spirit they have comes from God. For there are many false prophets in the world. 2 This is how we know if they have the Spirit of God: If a person claiming to be a prophet acknowledges that Jesus Christ came in a real body, that person has the Spirit of God. 3 But if someone claims to be a prophet and does not acknowledge the truth about Jesus, that person is not from God. Such a person has the spirit of the Antichrist, which you heard is coming into the world and indeed is already here.

Resources:
A Sermon on this Subject