For the phrase “On that day the root of Jesse shall stand as a signal to the peoples; the nations shall inquire of him,” see Romans 15:12.

Note that this quote in the New Testament is not taken from the Hebrew Bible but from the Greek Septuagint (LXX) which translates into English as “And there shall be on that day the root of Iessai, even the one who stands up to rule nations; nations shall hope in him.” (Translation by NETS — for the Greek version see the title’s tooltip)