Narrated Al-Miswar b. Makhramah:
'Umar consulted the people about the compensation of abortion of woman. Al-Mughirah b. Shu'bah said: I was present with the Messenger of Allah (ﷺ) when he gave judgement that a male or female slave should testify you. So he brought Muhammad b. Maslamah to him. Harun added: He then testified him.
Imlas means a man striking the belly of his wife.
Abu Dawud said: I have been informed that Abu 'Ubaid said: It (abortion) is called imlas because the woman causes it to slip before the time of delivery. Similarly, anything which slips from the hand or from some other thing is called malasa (slipped).
