# strengthen your hearts, so that they will be
Here "heart" is a metonym for one's beliefs and convictions. Alternate translation: "strenghten you, so that you will be" (See: [[rc://en/ta/man/translate/figs-metonymy]])
# at the coming of our Lord Jesus
"when Jesus comes back to earth"
# with all his holy people
"with all those who belong to him"