Surah Al-Baqarah 2:233

۞ وَٱلْوَٰلِدَٰتُ يُرْضِعْنَ أَوْلَـٰدَهُنَّ حَوْلَيْنِ كَامِلَيْنِ ۖ لِمَنْ أَرَادَ أَن يُتِمَّ ٱلرَّضَاعَةَ ۚ وَعَلَى ٱلْمَوْلُودِ لَهُۥ رِزْقُهُنَّ وَكِسْوَتُهُنَّ بِٱلْمَعْرُوفِ ۚ لَا تُكَلَّفُ نَفْسٌ إِلَّا وُسْعَهَا ۚ لَا تُضَآرَّ وَٰلِدَةٌۢ بِوَلَدِهَا وَلَا مَوْلُودٌ لَّهُۥ بِوَلَدِهِۦ ۚ وَعَلَى ٱلْوَارِثِ مِثْلُ ذَٰلِكَ ۗ فَإِنْ أَرَادَا فِصَالًا عَن تَرَاضٍ مِّنْهُمَا وَتَشَاوُرٍ فَلَا جُنَاحَ عَلَيْهِمَا ۗ وَإِنْ أَرَدتُّمْ أَن تَسْتَرْضِعُوٓا۟ أَوْلَـٰدَكُمْ فَلَا جُنَاحَ عَلَيْكُمْ إِذَا سَلَّمْتُم مَّآ ءَاتَيْتُم بِٱلْمَعْرُوفِ ۗ وَٱتَّقُوا۟ ٱللَّهَ وَٱعْلَمُوٓا۟ أَنَّ ٱللَّهَ بِمَا تَعْمَلُونَ بَصِيرٌ

Mothers may nurse [i.e., breastfeed] their children two complete years for whoever wishes to complete the nursing [period]. Upon the father is their [i.e., the mothers'] provision and their clothing according to what is acceptable. No person is charged with more than his capacity. No mother should be harmed through her child, and no father through his child. And upon the [father's] heir is [a duty] like that [of the father]. And if they both desire weaning through mutual consent from both of them and consultation, there is no blame upon either of them. And if you wish to have your children nursed by a substitute, there is no blame upon you as long as you give payment according to what is acceptable. And fear Allāh and know that Allāh is Seeing of what you do.

Translation: Saheeh International

Tafsir

Mothers shall suckle their children for two full years kāmilayn ‘two full ones’ is an adjective for emphasis; this is for such as desire to fulfil the suckling and this is the maximum length of time. …

Excerpt from Tafsir al-Jalalayn, commentary on 2:233, via Quran.com. The reader has the full commentary and 9 more tafsirs.