The ailment of man is his sin. Jesus spoke of himself as a physician who could provide a remedy for man's sin (Matt. 9:10-13). God's remedy for man's plight is prescribed through His Son (Heb. 1:1-2).
The only remedy for sin is God's word. The gospel is God's power to save (Rom. 1: 16). The word is able to make one wise unto salvation (2 Tim. 3:15); the word is able to save one's soul (Jas. 1:21).
The divine instruction, therefore, to gospel preachers is to "preach the word" (2 Tim. 4:2). There often are those kind-hearted souls who want to advise the preacher as to what to preach. Philosophy, psychology, economics, astronomy, etc., cannot save. God's word must be preached.
Not only must the word be preached, it must be "fully preached" (Rom. 15:19). Paul received great consolation out of the fact that he had declared "the whole counsel of God" (Acts 20:27). So long as a preacher is preaching any part of God's word, when that word is handled aright, he is doing precisely what God prescribed that he should do.
Brethren in some places think that preaching on some biblical themes will cause trouble. Preachers are therefore asked not to preach on divorce in some areas. At other places preachers are kindly advised that they should not teach on the mission of the church, the organization of the church, or the all-sufficiency of the church. Such preaching might cause trouble, some brethren believe.
On the contrary, the only way to solve the problems of men or churches is to preach the whole counsel of God. In fact, any time any part of God's word cannot be preached in any church, that church is not apt to have trouble — IT ALREADY HAS TROUBLE!!
A preacher might as well agree to preach something manifestly not taught in God's word as to agree not to preach something that is taught in the scripture. Preaching less than the whole counsel is the same type of sin as to preach more than God's will (Deut. 4:2; Rev. 22:18-19)
Not only has God prescribed what should be preached, he also has given explicit instruction as to how his word should be spoken. After appropriate prayer, Peter and John preached the word "with boldness" (Acts 4:31). Peter used the sword of the Spirit so effectively that it cut the hearers to tile heart (Acts 2:37; Cf Acts 5:33). Paul commanded young Timothy to "reprove, rebuke, and exhort" (2 Tim. 4:2) as he preached. Titus was told to "reprove them sharply" (Titus 1: 13}.
Paul adds that the truth should be spoken "in love" (Eph. 4:15) No matter how carefully one may preach, when he preaches the whole counsel of God, he is apt to be charged by some with not preaching in love. Some inside and some outside the church think that when certain truths are taught, one undoubtedly must have forgotten Paul's admonition. But while we emphasize the manner in which one must preach (i. e. "in love"}, we must never forget that the same passage obligates one to preach the "truth," and this certainly embraces all the truth.
God knew man's plight, and through His Son, he prescribed the only means of solving man's problem. And it matters not whether it be a problem of sinful man outside the church, or some problem that might arise within the church, God's prescription is the same THE WHOLE COUNSEL OF GOD MUST BE PREACHED IN THE MANNER IN WHICH GOD COMMANDED.