I recently heard someone making the case that certain things Jesus said only pertained to the apostles that He was speaking to at the time.
To folks to hold this view, I would refer them to Mt 28:20
Mt 28:20 teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. Amen.
We see that Jesus told the apostles to teach others to “observe all things whatsoever I have commanded you”.
So even if Jesus was just speaking to the apostles at a particular time, the instructions for the apostles was to teach disciples to do the same thing Jesus had instructed them to do. That includes disciples teaching other disciples to do all the things Jesus instructed.
All things the apostles were instructed in is also applicable to all believers today.