O Radix Jesse, qui stas in signum populorum, super quem continebunt reges os suum, quem gentes deprecabuntur: veni ad liberandum nos, jam noli tardare.
From the Eleventh Chapter of the Book of the Prophet Isaiah:
And there shall come forth a rod out of the stem of Jesse, and a Branch shall grow out of his roots:
And the spirit of the LORD shall rest upon him, the spirit of wisdom and understanding, the spirit of counsel and might, the spirit of knowledge and of the fear of the LORD . . . .
O Root of Jesse, who stands for an ensign of the people, before whom kings shall keep silence and unto whom the Gentiles shall make supplication: Come to deliver us, and tarry not.