"Glory to Allah, Who created in pairs all things that the earth produces, as well as their own (human) kind and (other) things of which they have no knowledge." - Quran 36:36 (read more)

"Narrated Kurib: the freed slave of Ibn 'Abbas, that Maimuna bint Al-Harith told him that she manumitted a slave-girl without taking the permission of the Prophet. On the day when it was her turn to be with the Prophet, she said, "Do you know, O Allah's Apostle, that I have manumitted my slave-girl?" He said, "Have you really?" She replied in the affirmative. He said, "You would have got more reward if you had given her (i.e. the slave-girl) to one of your maternal uncles." - Sahih Bukhari 3:47:765 (read more)

"It is obligatory to distribute one's zakat among eight categories of recipients (O: meaning that zakat goes to none besides them), one-eighth of the zakat to each category... The seventh category is those fighting for Allah, meaning people engaged in Islamic military operations for whom no salary has been allotted in the army roster (O: but who are volunteers for jihad without remuneration)." - Ahmad ibn Naqib al-Misri