"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)

"Even if they [kafir] give you some of your rights by treating you nicely, they do not give Allaah His rights and they do not give the Qur’aan its rights and they do not give our Prophet (peace and blessings of Allaah be upon him) his rights. The rights of Allaah and His Book and His Prophet are more important than our personal rights. Remember this, for this is one of the things that will help you to hate them and regard them as enemies until they believe in Allaah alone." - Islam Q&A