Why does Phineas stop to help Tom Loker? What do you think is going to happen to Tom in the Quaker house?

Phineas stops becaue it's the right thing to do. He is a Quaker. When he gets back to Phineas' home, he will be well taken care of.

"Well if I hadn't thee would have pushed us down, thee sees," said Phineas, as he stooped to apply his bandage. "There, there, -- let me fix this bandage. We mean well to thee; we bear no malice. Thee shall be taken to a house where they'll nurse thee first rate, well as thy own mother could."