﴿ وَإِنْ خِفْتُمْ أَلَّا تُقْسِطُوا۟ فِى ٱلْيَتَٰمَىٰ فَٱنكِحُوا۟ مَا طَابَ لَكُم مِّنَ ٱلنِّسَآءِ مَثْنَىٰ وَثُلَٰثَ وَرُبَٰعَ ۖ فَإِنْ خِفْتُمْ أَلَّا تَعْدِلُوا۟ فَوَٰحِدَةً أَوْ مَا مَلَكَتْ أَيْمَٰنُكُمْ ۚ ذَٰلِكَ أَدْنَىٰٓ أَلَّا تَعُولُوا۟ ﴾

“And if you have reason to fear that you might not act equitably towards orphans, then marry from among [other] women such as are lawful to you - [even] two, or three, or four: but if you have reason to fear that you might not be able to treat them with equal fairness, then [only] one - or [from among] those whom you rightfully possess. This will make it more likely that you will not deviate from the right course.”

Please check ayah 4:4 for complete tafsir.