Adam Clarke on 2 Thessalonians 3:6

That ye withdraw yourselves - Have no fellowship with those who will not submit to proper discipline; who do not keep their place; ατακτως, such as are out of their rank, and act according to their own wills and caprices; and particularly such as are idle and busybodies. These he had ordered, 1Thes 4:11, 1Thes 4:12, that they should study to be quiet, mind their own business, and work with their hands; but it appears that they had paid no attention to this order, and now he desires the Church to exclude such from their communion.

And not after the tradition - This evidently refers to the orders contained in the first epistle; and that first epistle was the tradition which they had received from him. It was, therefore, no unwritten word, no uncertain saying, handed about from one to another; but a part of the revelation which God had given, and which they found in the body of his epistle. These are the only traditions which the Church of God is called to regard.