Sura An-Nisa (سورة النساء) verse 3

Sura An-Nisa (سورة النساء) verse 3

وَ إِنْ خِفْتُمْ أَلاَّ تُقْسِطُوا فِي الْيَتامى‏ فَانْكِحُوا ما طابَ لَكُمْ مِنَ النِّساءِ مَثْنى‏ وَ ثُلاثَ وَ رُباعَ فَإِنْ خِفْتُمْ أَلاَّ تَعْدِلُوا فَواحِدَةً أَوْ ما مَلَكَتْ أَيْمانُكُمْ ذلِكَ أَدْنى‏ أَلاَّ تَعُولُوا 

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.