Who is Jacob from The Contract with God Trilogy: Life on Dropsie Avenue and what is their importance?

Jacob is Rifka's elderly husband and the father of their two children, Rebecca and Daniel. He is a carpenter by trade, and he is known as a kind and caring man. When he finishes a five-year project at the Synagogue for a study hall, he believes he no longer has a reason to live. He discusses such philosophy with a cockroach in the alley outside his building, and goes inside for dinner. He is hired by Rabbi Bensohn to build a room for the Rabbi's wife, and to do this, he partners with Angelo, an Italian immigrant who is also a carpenter.