Surah An-Nisa — Ayah 3 (4:3)
وَإِنۡ خِفۡتُمۡ أَلَّا تُقۡسِطُواْ فِي ٱلۡيَتَٰمَىٰ فَٱنكِحُواْ مَا طَابَ لَكُم مِّنَ ٱلنِّسَآءِ مَثۡنَىٰ وَثُلَٰثَ وَرُبَٰعَۖ فَإِنۡ خِفۡتُمۡ أَلَّا تَعۡدِلُواْ فَوَٰحِدَةً أَوۡ مَا مَلَكَتۡ أَيۡمَٰنُكُمۡۚ ذَٰلِكَ أَدۡنَىٰٓ أَلَّا تَعُولُواْ ٣
English translation (Saheeh International)
And if you fear that you will not deal justly with the orphan girls, then marry those that please you of [other] women, two or three or four. But if you fear that you will not be just, then [marry only] one or those your right hands possess [i.e., slaves]. That is more suitable that you may not incline [to injustice].
Brief commentary
If you fear that you will not be just in marrying the female orphans under your guardianship – fearing that you will not give them an appropriate dowry or will not treat them well – then do not marry them, and marry other women you choose. You may marry two, three or four; but if you fear that you will be unjust between them, then marry just one, or suffice with what you possess of slave women, for their rights are not the same as the rights of wives. This is the best way to avoid being unjust or biased.