The Tears of Andraste is a legendary relic, and one of the holiest relics in history. According to the legend, before the Maker spoke to her, she despaired at the fate of her fellows. At that time, every night, Maferath would come to console her and each time Andraste would tell him her despair while shedding a single tear which Maferath captured in a vial. In the thirtieth night the vial was full and when dawn came Andraste saw her first vision of the Maker.
Even though this legend is popular and has passed on for ages, a part of it isn't in the Chant of Light. The relic allegedly ended up to the Bann of West Hill and then passed on to his son, Bann Franderel.
This plot item can be given to Slim Couldry in order to return them to the Chantry as an anonymous donation or the Warden can tell Slim that they will donate the tears themselves or the Warden can keep the tears for themselves.