Why Abraham and Muhammad were important to Islam?

Abraham was a Semite and Hebrew. He was called by God to be the father of the nation who would bring forth the seed that was promised to Eve to save man. He obeys God, God made promises with him.
Land, Great Nation, Seed, Blessing to all nations
He was known for his great faith.

Muhammad was born in Mecca approximately 570 C.E. and was a member of the Quraysh tribe. As with Moses and Jesus, we know little about his childhood. His parents died when he was young, and he never learned to read or write. When he was 12, he visited Syria and had his first exposure to Jews and Christians and apparently developed a respect for these "People of the Book." At 25, Muhammad married a widow named Khadija who was involved in trade and got him involved in it as well.

During one trading journey when he was about 40, Muhammad had an encounter with the angel Gabriel revealed to him special revelations. Different opinions exist on whether Mohammed miraculously