4 by which, when you read, you may understand my knowledge in the mystery of Christ),
4 by which,
We can translate “by which” as in accordance with which, referring to the first two chapters.
when you read,
By public reading the Ephesians would be able to understand the nature of the new revelation of the church.
you may understand my knowledge [insight]
The word “knowledge” means insight. The word carries the idea of bringing together. We need to bring together various ideas in order to understand or comprehend fully what the church is about. Insight into truth is an important concept to grasp before we apply it to experience. Lack of spiritual discernment is the opposite of insight.
in the mystery of Christ),
The biblical word for “mystery” does not refer to something unknowable but to a truth not revealed to this point. It is a truth known only to those to whom it is revealed. The “mystery of Christ” was not known before the day of Pentecost.
The third chapter of Ephesians uses the word “mystery” four times. Paul also used it in 1:9 and 5:32. The New Testament uses the term “mystery” 27 times, referring to 11 separate mysteries. In 1:9 Paul spoke of the “mystery” of God’s will. He gave details of that mystery in 2:14-15; the mystery of Christ is that He is the head of a new society of people called the church (Co 1:26).
Ro 16: 25 Now to Him who is able to establish you according to my gospel and the preaching of Jesus Christ, according to the revelation of the mystery kept secret since the world began
We must know truth before we can apply it.
Much of the church today operates on lack of spiritual discernment. Discernment requires knowledge. Biblical knowledge will help us identify false ideas and untruths. We cannot live the Christian life without understanding the principles upon which it stands.