"And if you fear that you cannot act equitably towards orphans, then marry such women as seem good to you, two and three and four; but if you fear that you will not do justice (between them), then (marry) only one or what your right hands possess; this is more proper, that you may not deviate from the right course." - Quran 4:3 (read more)

"Narrated Abdullah ibn AbuDhubab: Iyas ibn Abdullah ibn AbuDhubab reported the Apostle of Allah (peace be upon him) as saying: Do not beat Allah's handmaidens, but when Umar came to the Apostle of Allah (peace be upon him) and said: Women have become emboldened towards their husbands, he (the Prophet) gave permission to beat them." - Sunan Abu Dawud 11:2141 (read more)

"Islam says that these three groups [Jews, Christians, and Magians] may be given the choice: they may enter Islam or they may pay the jizyah and feel themselves subdued. Some of the scholars are of the view that others may also be given the choice between Islam and jizyah, but the most correct view is that no others should be given this choice, rather these three groups are the only ones who may be given the choice, because the Prophet (peace and blessings of Allaah be upon him) fought the kuffaar in the Arabian Peninsula and he only accepted their becoming Muslim." - Islam Q&A