Translation:

3. If ye fear that ye shall not be able to deal justly with the orphans marry women of your choice two or three or four; but if ye fear that ye shall not be able to deal justly (with them) then only one or (a captive) that your right hands possess. That will be more suitable to prevent you from doing injustice.

Notes (Tafseer)

508. Notice the conditional clause about orphans, introducing the rules about marriage. This reminds us of the immediate occasion of the promulgation of this verse. It was after Uhud, when the Muslim community was left with many orphans and widows and some captives of war. Their treatment was to be governed by principles of the greatest humanity and equity. The occasion is past, but the principles remain. Marry the orphans if you are quite sure that you will in that way protect their interests and their property, with perfect justice to them and to your own dependents if you have any. If not, make other arrangements for the orphans.

539. As the woman in marriage surrenders her person, so the man also must surrender at least some of his property according to his means. And this gives rise to the law of Dower. A minimum dower is prescribed, but it is not necessary to stick to the minimum, and in the new relationship created, the parties are recommended to act towards each other with the greatest confidence and liberality.