The preaching of the law as oppose to the good wholesome preaching of the grace of God in Christ Jesus. "Thou shalt not" 3 of the most powerful incentives to the human flesh to sin that there were.
Uh, I'd have to disagree there! It's God's "law." How unwholesome can it be? Wishy-washy "do what your heart desires" preaching is more to blame. God said don't do it, so I don't! I look at it more as God's instructions to me to holy living; how to walk before a holy God.
1 John 3:4 (ESV) Everyone who makes a practice of sinning also practices lawlessness; sin is lawlessness.
We need more pastors today warming the pews, preaching against sin and, yes, preaching from the "law." I'm going to say the real problem is a lack of "Hell-fire-and-brimestone burn the chaff and see who remains" preachers giving us God's instructions so we know how to live holy lives. And that means preaching the "law," balanced by the gospel.
The real problem with what you say is that without the "law" there is no need for grace! If God never said "don't," then what is there to forgive when you do? Grace was as abundant in the OT as in the New. Without it all would have ended with Adam. The patriarchs were all extended grace when they failed. And even David was extended grace after committing sexual sin with Bathsheba and compounding that by having her husband killed! Was that grace not wholesome?
My Bible has 66 books, all the inspired word of God. I am loath to do away with any of them, especially the first 5 books of the law wherein I clearly see what is expected of me. So yes, preach grace, but preach it correctly. Preach that it all comes together in the person of Jesus. But preach also the "law," because without it grace is meaningless. And if you believe as I do that Jesus is God, and if you believe God spoke to Moses "face to face" (Exodus 33:11) and that it was God who gave Moses the "law," then those first 5 books are extremely important "to the good wholesome preaching of the grace of God in Christ Jesus."