1. III. Truth Will Not Associate With Deception (7-11)
    1. B. The Deception of Exceeding Christ's Message (9)

Matthew Henry

9
To leave the doctrine of Christ is to leave God, for that doctrine is the only appointed means to guide us to God. Adherence to the truth unites us to Christ, and so to the Father. His doctrine gives us knowledge of Father and of Son, sanctifying us, so that we will be prepared to receive the love of Father and Son, and for an eternity of enjoying them. (Jn 15:3 - Christ's word cleanses us.)
 
 

Adam Clarke

9
 Transgression, here, indicates a going beyond the prescribed limits, which were set by God. This is the danger of excess that unruled passion leads us into. This unruliness shows us to be lacking the abiding presence of the Father. By contrast, the one that abides within His prescribed limits has made his body the temple of the Holy Trinity, with which he has constant communion.
 
 

Barnes

9
The doctrine of Christ could be taken as meaning that which He taught, or that which is taught with regard to Him. In either case, it is essential that a true understanding of the precepts, character, and work of our Savior be had. Those that do not hold to this true understanding do not truly know God. (Jn 1:18 - for Christ is the One who explains the Father to us. Jn 5:23 - Not to honor the Son is not to honor the Father. Jn 15:23 - To hate Him, is to hate the Father. Jn 17:3 - Eternal life consists of knowing both the Father and the Son. 1Jn 2:23 - In denial or in confession, the Son and the Father are united. Either way, the treatment of one determines the treatment of the other.) Holding to true doctrine is essential to true piety. The Father and the Son are so closely united that true understanding of the one will bring with it true understanding of the other. (Jn 14:7 - to know Jesus is to know the Father. Jn 14:9-11 - To see Him is to see the Father, for they are each in the other.)
 
 

Wycliffe

9
When other teachers present themselves to our hearing, our examination of them is to be based on their teaching of Christ. If they profess Christianity, but don't remain true to the doctrine He taught, they are false. If they remain true to His doctrine, then they are true.
 
 

Jamieson, Fausset & Brown

9
Not abiding in the doctrine of Christ results in the loss of God's presence. Such will tend to try and take the lead away from Jesus, as they teach their own thoughts. (Jn 10:4 - The sheep follow the true shepherd because they know his voice. 3Jn 9 - The false teacher will attempt to keep truth from being heard. 1Jn 2:23 - In denying the Son, they have denied also the Father.)
 
 

New Thoughts

How essential it is to have a solid knowledge of the true doctrine of the Gospel! Without it, we can have no means of verifying any other teaching we hear. And experience shows that without the Holy Spirit to guide us, we can't even understand that Gospel, it's real meaning won't be clear to us. Oh, God! I thank You that You have raised up in me a desire to understand, a desire to learn from Yourself, and from those who have understood You so well. I thank You that where opinions have confused the truth, coming down on every side of it, You reveal the true answers. I thank You for the questions that remain unanswered for now, for I know that when the time is right, You will make my answers clear. I thank You for all the new insights You have been giving to me throughout these times together - insights into both Your character, and my own. I continue to pray that You would make those two characters more alike than they presently are, for it pains me more each day to realize how vastly I differ from Your plan. Lord, You've given me a difficult assignment in raising this family. My understanding is still so incomplete, and yet it is my duty to guard them from error. How, Lord? I can only pray that You would keep me from anger when those You have appointed me to protect question that very protection. I can only pray that You give me the wisdom and humility to fill that office as You desire. Lord, I've seen myself, and found me wanting. I don't take well to being questioned, do I? Even requests for explanation hit me like an accusation of wrong. Why, God? Am I so insecure? I see it is so. Help me to find my security in You, knowing that Your wisdom is my guide in all things. Help me to grasp hold of that concept of leaning not on my own understanding. Help me to recognize whether it's Your truth or my own concoction that I'm struggling to uphold, for my eyes deceive me too often. All that I am is in Your hands, Lord. You know that, and I know that. But too often, I forget it. Help my memory where it truly matters. I don't want to be found getting out ahead of You, nor do I want to lag behind. I want to be where You have placed me. I do. Why, then, do I find it so hard to do? The flesh is so weak, Lord, so weak. Strengthen me to Your will.