What did Silas do for Sally Oates in Silas Marner?
In order to relieve her symptoms of dropsy, Silas Marner charitably administers to Sally Oates some foxglove, a liquid which eases her pain.
Unfortunately for the newcomer to Raveloe, Silas Marner's hopes of opening up "some possibility of fellowship with his neighbors" by relieving the discomfort of the cobbler's wife brings only negative consequences. For after he has cured the symptoms of Mrs. Oates, he finds mothers at his door for a cure for whooping-cough, men for something for their rheumatism or their arthritis, all of whom carry silver in their hands. Never one for falsities, Marner tells them he cannot cure them; however, no one will believe him. After Marner turns them away, they blame attacks of their symptoms on him.
Thus it came to pass that his movement of pity towards Sally Oates, which had given him a transient sense of brotherhood, heightened the repulsion between him and his neighbors, and made his isolation more complete.
Marner becomes more and more reclusive. He begins to withdraw from society, instead working more hours and counting his gold.
He began to think it [the money] was conscious of him, as his loom was, and he would on no account have exchanged those coins...for other coins with unknown faces.
Year after year, Marner lives in this state of exile and rejection. After working all day, he counts his gold, bringing it from a hole in his floor and counting it fondly.
On Chapter II, Part 1 we find the character of Sally Oates, a cobbler's wife, who was sitting by the fire suffering from symptoms of "heart disease and dropsy" which reminded him of the symptoms his own mother experienced prior to dying. Silas remembered that a certain concoction made of "foxglove" which is referred to as "the stuff".
Silas remembered that such concoction made his mother believe that she was getting better, and (in order to ease Sally's pain), he brought her some of "the stuff" and held a high esteem in Sally's eyes since it did the same effect on Sally as it did with Silas's mother. The only condition was that the woman could not tell the local doctor about what Silas was doing because (as expected) the doctor did not agree with those local cures that play with the psyche of others.