# You should go and learn what this means

Jesus is about to quote the scriptures. Alternate translation: "You should learn what God meant when he said this"

# For I came

Here "I" refers to Jesus.

# the righteous

"righteous people." Jesus knew that some people thought that they were righteous even though they were not. Alternate translation: "those who think they are righteous" 

# but sinners

"but I came to call sinners to repent"