Jamieson, Fausset and Brown on 1 Corinthians 2:4

4. my speech--in private.

preaching--in public [Bengel]. Alford explains it, My discourse on doctrines, and my preaching or announcement of facts.

enticing--rather, "persuasive."

man's wisdom--man's is omitted in the oldest authorities. Still "wisdom" does refer to "man's" wisdom.

in demonstration of ... Spirit, &c.--Persuasion is man's means of moving his fellow man. God's means is demonstration, leaving no doubt, and inspiring implicit faith, by the powerful working of the Spirit (then exhibited both outwardly by miracles, and inwardly by working on the heart, now in the latter and the more important way only, Mt 7:29; Ac 6:10; He 4:12; compare also Ro 15:19). The same simple power accompanies divine truth now, producing certain persuasion and conversion, when the Spirit demonstrates by it.