If something important risks being spoiled, it must be preserved. Satan wants truth corrupted. The means by which he most often accomplishes this is by introducing some error into the truth. The gospel as truth is the power of God into salvation (Rom. 1:16; 1 Tim. 2:4). We are sanctified by the truth (John 17:17). The truth makes us free (John 8:32). Very bad consequences result from altering the truth. Satan's strategy of changing the truth is seen in his temptation of Eve (Gen. 3) and of the Lord Jesus (Mt. 4). Paul identifies "chang[ing] the truth of God into a lie" as foundational to apostacy (Rom. 1:25). God has promised the preservation of the truth (Matthew 5:18; 24:35; etc.). For everything that God is doing, He expects cooperation from us, even so that we will reveal to Him our belief in His plan. A major feature of the God's moral will for mankind is the keeping or guarding of His truth. God wants His people especially to preserve Godly, Scriptural doctrine and practice for the next generation of His people. When that responsibility is not faithfully accomplished by His people, false doctrine and practice will flourish to the destruction of men's souls.
I could spend some time showing you from the Bible how important this task is by looking at every time the words "keep, keepeth, kept" etc. are used in the OT and NT. One could argue that not doing this led to Israel's downfall. One could also contend that this is the theme of the entire epistle of Jude.
Assuming that it is very important, how is it to be done? God has an ordained means by which the truth is preserved intact for the next generation. The most important aspect in this job of keeping is the container for truth. Without keeping truth in the proper container, truth will become contaminated. I am convinced that this is the chief reason for the widespread doctrinal and practical corruption in the U.S. and the world. A part of Satan's plan for destruction of truth has centered on replacing the God-designed container and replacing it with one of his own liking that is purposefully deficient. Men have even sincerely gone about preserving the truth using the inferior repository, so were doomed to failure from the start.
[Tomorrow I will reveal the only genuine safeguard of truth and the hole-ridden, faulty one.]