This verse either means something very specific or it doesn’t. How can I tell what it means?
If I ask 10 people, 8 won’t have any idea and 2 will be just making it up or won’t agree.
Put it in context to understand it. If your respondants are clueless, tell them the context here.
So whats happening? What part of the life of Jesus are we up to here?
Jesus, after Crucifixion, has risen on the third day, continued teaching the Apostles and doing His work. He asks the Apostles to meet Him in Galilee.
The Apostles meet Jesus in Galilee. Jesus tells them He has been given all the Authority in Heaven and on Earth. Jesus then tells the Apostles to go forth and make disciples of all nations and Baptise them in the name of the Father and the Son and the Holy Spirit.
And (here is your passage) then Jesus tells the Apostles to
“Teach them (the disciples of all nations that the Apostles have Baptised) to observe all the commands I gave you”
So this verse is Jesus specifically telling the Apostles what to teach, ie all the commands He had given the Apostles.
If I want to know those commands, I would read the Gospels.
And (here is something to think about) perhaps Jesus gave the Apostles commands to teach us to observe that were not recorded. But we observe them because the Apostles first taught us, and so does the Church.
A learned Theologican might help us out here, as I am still just learning the Gospels.
So a quick glance at the Gospels tells me ( from the meeting with Lazarus, Martha and Mary) that Jesus said the two most important Commandments are?