Hagar plays a very important role in the identity of the Arab people as a mother of Ishmael she is considered to be mother of all Arabs. The prophet Muhammad was a direct descendant of Ishmael from the line of Kedar one of Ishmael's sons.
Sahih Bukhari 4.577-578; Sahih Bukhari 7.21
The tyrant then gave Hajar as a girl-servant to Sarah. Sarah came back
(to Ibrahim) while he was praying. Ibrahim, gesturing with his hand,
asked, "What has happened?" She replied, "Allah has spoiled the evil
plot of the infidel and gave me Hajar for service." Abu Huraira then
addressed his listeners saying, "That (Hajar) was your mother, O you Arabs, the descendants of Ishmael, Hajar's son".