In a word directed to preachers/pastors, Luther provides some wonderful counsel we can all use to evaluate the content of the sermons we are hearing and books we are reading. The touchstone? Jesus Christ, of course:
The book of 1 Peter is a wonderful letter and a model for us. Peter begins by explaining who Christ is and what we have received through him. he says that God has given us a new birth to a living hope through Christ’s resurrection. Likewise, the Father out of pure mercy has given us everything, apart from our merit. These are genuinely evangelical words that must be preached.
May God help us. How little of this message we find in other books! Even among the best, such as those written by Jerome and Augustine, we find hardly anything. Therefore, we must preach about Jesus Christ, that he died and rose from the death and why he died and was resurrected. We must preach so that the people will believe in him and through faith be saved.
This is what it means to preach the true gospel. Any preaching that is different than this is not the gospel, no matter who preaches it.
(from Faith Alone: A Daily Devotional / LW 30:9)
If, in our churches, devotional lives, and personal reading, we find that our preaching/teaching centers on anything other than Christ crucified and risen for us…we would do well to seek out the genuine gospel elsewhere!