This quest is available after you speak to Zealot Ware, who has asked you to speak to Brother Devin and convince him to end his fast.
Speak to Devin and convince him you are the messenger he's been waiting for and to give up his fast.
Return to Zealot Ware and let him know the good news. He will reward you with some Ware's Brew, a beverage that will reduce rads and increase HP. He will also provide you with the recipe and that you're welcome to some more whenever he makes a new batch.