The sword of God's truth!
(Arthur Pink, "Faithfulness")
"Their speech is filled with flattery." Psalm 5:9
This is the identifying mark of the "hireling," the false pastor. He aims at pleasing his hearers, making them feel satisfied with themselves, ever patting them on the back.
"But he who has My Word — let him speak My Word faithfully" (Jeremiah 23:28) — no matter how unpalatable it may be to the flesh, how much of a weariness to those who wish to have their ears tickled with novelties, or how loud the outcry against it is!
Ministerial faithfulness includes . . .
  loyalty to his Master,
  devotion to His interests,
  steadfast adherence to the preaching of His Word,
  dispensing the truth unto those whose souls are committed to Him,
  not mixing it with his speculations, much less substituting false doctrine.

A far higher motive than the pleasing of his hearers must actuate and regulate ministerial service.

Faithful preaching
will render the minister unpopular, and will empty churches — not fill them!
"Then you will know the truth — and the truth will set you free." (John 8:32) Souls are caught fast in the meshes of Satan's lies — and nothing but the sword of God's truth can cut them free!
"A faithful man — who can find?" (Proverbs 20:6). Why is this? Because it is the part of fallen human nature to take the line of least resistance, and choose the path easiest to the flesh. But remember, my reader, whoever you are, that, "Lying lips are abomination to the Lord — but those who deal faithfully are His delight." (Proverbs 12:22)
"Be faithful unto death — and I will give you a crown of life!" (Revelation 2:10)

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For further reading: John Angell James, "Our sins at the seminary".