Why was slavery not forbidden in Islam, and how is it permissible to cohabit with a slave woman without marriage, and does she have the right to choose her husband?

The perfection of Allah's knowledge, mercy, and wisdom necessitated the legislation of Jihad to achieve justice, security, and the protection of lives. Enslavement of captives was legislated as a remedy for their corruption and a purification for them, where the Imam has the choice between executing the captive, pardoning them, ransoming them, or enslaving them. This is because their presence among Muslims might lead to their reform, guidance, and acceptance of Islam, subsequently leading to their liberation through manumission contracts (kitaba) or various forms of freeing. Thus, enslavement in Islam is a means of reforming the enslaved and liberating them. It is established that the master has rights over his enslaved concubine, and if she bears him a child, she becomes an "umm walad" (mother of a child) who cannot be sold, and her children are free. Furthermore, the marriage of a free man to an enslaved woman is not permissible except under specific conditions. Allah possesses ultimate wisdom in His legislation.