The Lord said to Jeremiah that he was a prophet to the nations, to which Jeremiah said he was only a young man, and so did not believe that he could do the job.
However, the Lord told the young prophet not to think on his youthfulness, but to speak fearlessly whatever the Lord said to speak.
Watch what Yahweh God did next,
“Then the LORD put forth His hand and touched my mouth, and the LORD said to me: ‘Behold, I have put My words in your mouth. See, I have this day set you over the nations and over the kingdoms, to root out and to pull down, to destroy and to throw down, to build and to plant’” (Jeremiah 1:9-10).
Did you see that? God with His hand touched the mouth of the prophet! Therefore, he could speak the word of God boldly to anyone.
The Lord does not have to touch our mouths literally, but we do have His word and if we speak it, it will do its job. Do not think about yourself when contemplating teaching another person, but focus on God’s word.