When Jesus said “Get thee behind me Satan, He was not talking to Peter. he was talking to a religious spirit that spoke to Him through the mouth of Peter. Peter was not yet born again but he was certainly one of the elect. so I say to you if the enemy can speak words through Peter of all people, he can also speak through us to both others and to ourselves. Paul explained it to the Ephesians when he warned that the battle is not between us and other human beings. it is between us and the principalities and powers that others have yielded to by walking in the flesh and unknowingly made invitations to demons in the process.
so check this out from Jessie Penn-Lewis in her amazing book, /war on the Saints, written over a century ago::
In the unregenerate man the will is enslaved to Satan, but in the man who has been regenerated, and delivered from the power of sin, the will is liberated to choose the things of God. In one who has thus been brought into fellowship with God, Satan can only gain ground by stratagem, or, in Bible terms, by “wiles”; for he knows he will never get from a believer deliberate consent to the entry, and control of evil spirits. The Deceiver can only hope to obtain that consent by guile: i.e., by feigning to be God Himself, or a messenger from Him. He knows, too, that such a believer is determined to obey God at all costs, and covets the knowledge of God above all else on earth. There is, therefore, no other way to deceive this one, but by counterfeiting God Himself, His presence and His workings; and under pretense of being God, to obtain the co-operation of the man’s will in accepting further deceptions; so as eventually to lead to “possession” of some part of the believer’s mind or body, and thus injure or hinder his usefulness to God, as well as that of others who will be affected by him.
As an example, parents don’t set out to hurt us. Yet if Satan has access to them, they will say things, think things and do things that hurt and even damage their offspring for years to come. in such instances, the enemy was working through them against their children. They did not know it but when they die, they will suffer immensely. Not necessarily in hell, but when they give an account before the throne of God.