Esto Mihi

The Introit for "Quinquagesima´s Sunday" (this year on February 14, the last Sunday after Epiphany) is Esto Mihi ("Be unto me"). Here's the mp3 (and a beautifully-sung version it is, too).

Here's a PDF of the score, from JoguesChant. And here's an image of it from the Benedictines of Brazil:

The text is from Psalm 31:

Be unto me a protecting God and a house of refuge, to save me; for you are my support and my refuge; and for the sake of your name you will lead me and nourish me. In you O Lord, do I trust; let me never be put to shame; deliver me in your righteousness.