If you preach by the power of the Spirit, you preach with sharpness. You preach sharply. This means clearly, plainly. It is so clear that it easily divides right from wrong in the mind of the listener.
The sharpness in you is the sharpness of the power of the word of God which is in you – see 2 Nephi 1:26.
Sharp is Not Necessarily Angry or Harsh
When you speak sharply, you are not necessarily speaking angrily – but you speaking very clearly, which people may choose to think is you being upset.
Also, this sharpness and power can be overwhelming to the point where it is almost impossible to stifle or bottle up – so that you end up going out to preach because it is the only way to stop your bones from quaking and to get that itch to stop itching.
Indeed, going out and preaching – with sharpness – is the only way sometimes to keep your clothes from getting stained with the blood of others – to keep yourself from being at least partially responsible for any bad decisions they may make.
See Alma 43:1, Ether 12:2, and Moses 6:31-34.
Alma 43:17 – And Moroni took all the command, and the government of their wars. And he was only twenty and five years old when he was appointed chief captain over the armies of the Nephites.
Notice the word only. Perhaps Moroni was quite a bit younger than the average chief Nephite military commander.
Yet Moroni proved to be a fearless leader. And when it came time, he knew how to use sharpness to cut through the skin and muscle of a situation and get right to its marrow. Just read Alma 60.
Reprove Betimes With Sharpness
See D&C 121.
Remember – the sharpness in Nephi when he corrected his brethren was not harshness, not necessarily loudness. It was the still small sharpness of the Holy Ghost – the clarity and plainness and unmistakability of the power and truth of God.
Seek to explain things clearly as a full-time missionary or when sharing the Gospel at any time – so clearly that those with whom you converse cannot misunderstand you. This is sharpness.
The word of God is the sharpest substance in the universe. That is, it is the clearest and brightest of all.