1 Corinthians 2:4-5
And I did not use persuasive words of [human] wisdom in my message and preaching, but they were [accompanied by] a demonstration of the Holy Spirit and power [from God]. [Note: This "demonstration" could have included the evidence of miraculous spiritual gifts which Paul utilized while there in Corinth. See 14:18].
2 Corinthians 10:4-5
For the weapons of our warfare are not like the world's [i.e., which rely on human ingenuity and unspiritual principles], but they are empowered by God to overthrow [Satanic] fortifications.
1 Peter 1:12
It was revealed to these prophets that you people, not they, were the ones being ministered to in the matters now being announced to you by those who preached the Gospel to you by the Holy Spirit, who was sent from heaven. [This message contained] things which angels would like to look into.