Out of context the following scripture seems to indicate that we are not allowed to teach anyone anything:

But you are not to be called rabbi, for you have one teacher, and you are all brothers. And call no man your father on earth, for you have one Father, who is in heaven. Neither be called instructors, for you have one instructor, the Christ. -- Matthew 23:8-10 ESV

The KJV translation replaces "teacher" and "instructor" with "master". In the context of Matthew 23, Jesus addressed the hypocritical Pharisees who gave themselves important titles and elevated themselves above the laymen. It is not so much what they taught that Jesus had a problem with, but more what they do that Jesus had a problem with:

The scribes and the Pharisees sit on Moses’ seat, so do and observe whatever they tell you, but not the works they do. For they preach, but do not practice. -- Matthew 23:2-3 ESV

Matthew concluded his book with the great commission from Jesus which is:

Go therefore and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, teaching them to observe all that I have commanded you. And behold, I am with you always, to the end of the age.” -- Matthew 28:19-20 ESV

From this we can see that Jesus instructed his disciples to teach what he commanded. Therefore, we should rather ask...

What did Jesus command?

Do not think that I came to destroy the Torah or the Prophets. I did not come to destroy but to complete. For truly, I say to you, till the heaven and the earth pass away, one yod or one tittle shall by no means pass from the Torah till all be done.

• Whoever, then, breaks one of the least of these commands, and teaches men so, shall be called least in the reign of the heavens;
• but whoever does and teaches them, he shall be called great in the reign of the heavens.

-- Mattithyahu / Matthew 5:17-19 (TS2009)

Then Jesus proceed with some of the commands as examples such as:

• murder (Matthew 5:21-22)
• reconciliation (Matthew 5:23-26)
• adultery (Matthew 5:27-30)
• divorce (Matthew 5:31-32)
• swearing (Matthew 5:33-36)
• trustworthiness (Matthew 5:37)
• retaliation (Matthew 5:38-48)

In addition, Jesus also commanded:

Teacher, which is the great command in the Torah?

And יהושע [Jesus] said to him, "

1. ‘You shall love יהוה your Elohim [God] with all your heart, and with all your being, and with all your mind.’ (Deuteronomy 6:5) This is the first and great command.
2. And the second is like it, ‘You shall love your neighbour as yourself.’ (Leviticus 19:18)

On these two commands hang all the Torah and the Prophets.

-- Mattithyahu / Matthew 22:36-40 (TS2009)

John also recalls that Jesus taught:

As the Father loved Me, I also have loved you; abide in My love. If you keep my commandments, you will abide in my love, just as I have kept My Father’s commandments and abide in His love. These things I have spoken to you, that My joy may remain in you, and that your joy may be full.

This is my commandment:

That you love one another as I have loved you.

Greater love has no one than this, than to lay down one’s life for his friends. You are My friends if you do whatever I command you. No longer do I call you servants, for a servant does not know what his master is doing; but I have called you friends, for all things that I heard from my Father I have made known to you. You did not choose me, but I chose you and appointed you that you should go and bear fruit, and that your fruit should remain, that whatever you ask the Father in my name He may give you. These things I command you, that you love one another.

-- John 15:9-17 (NKJV)