Ch. 1 – Be thankful for a brother-in-Christ whose faith is growing and love increasing.
Jesus will be “revealed from heaven with His mighty angels in flaming fire.” Where else in the Bible are angels associated with flaming fire?
Ch. 2 – The “lawless one” of the “rebellion” will be, or perhaps already is, one: 1) who claims he is God; 2) whose coming is satanic; 3) whose activity will be marked by false signs and wonders and deception; who is (or was/will be) believed by the faithless perishing ones; 5) and evidenced by the perishing ones having pleasure in unrighteousness.
It is okay to hold to good tradition – tradition that honors and brings glory to God.
Ch. 3 – Have nothing to do with an idle/lazy brother, that he may be ashamed. You can recognize that one by his not holding to the traditions of Paul’s example (of hard work, faith, love, hope, etc.). Note I Cor. 5:9-13, where Paul admonishes to not have anything to do with one who calls himself a brother while at the same time involved in sexual immorality, greed, idolatry, reviling, drunkenness, and swindling/cheating. Could these things be the defining characteristics of a brother who is idle? The one who is idle fills his life with things of the world, not with the things of God.