One was about the Doctrine of Balaam … what was it? I suggest it was a form of antinomianism, and related to the Nicolaitans:
“[The doctrine of Balaam] is stated in the subsequent part of the verse: ‘Who taught Balak to cast a stumbling-block before the children of Israel.’ … The meaning here is, that it was through the instructions of Balaam that Balak learned the way by which the Israelites might be led into sin, and might thus bring upon themselves the divine malediction. … The attitude of Balaam’s mind in the matter was this: i. He had a strong desire to do that which he knew was wrong, and was forbidden expressly by God. ii. He was restrained by internal checks and remonstrances, and prevented from doing what he wished to do. iii. He cast about for some way in which he might do it, notwithstanding these internal checks and remonstrances, and finally accomplished the same thing in fact, though in form different from that which he had first prepared. This is not an unfair description in what often occurs in the plans and purposes of a wicked man.”
Albert Barnes, Notes on … Revelation, pp. 75-76.
Christine’s note: Barnes makes a cogent case that Balaam’s sin was in obeying the letter of the law while violating the spirit of it.
“Compare Re 2:14, 15, which shows the true sense of Nicolaitanes; they are not a sect, but professing Christians who, like Balaam of old, tried to introduce into the Church a false freedom, that is, licentiousness; …”
Jamieson, Faussett, and Brown, Commentary, Revelation 2:6.