The Prophet ﷺ said, "Don't keep camels and sheep unmilked for a long time, for whoever buys such an animal has the option to milk it and then either to keep it or return it to the owner along with one Sa of dates." Some narrated from Ibn Seereen (that the Prophet ﷺ had said), "One Sa of wheat, and he has the option for three days." And some narrated from Ibn Seereen, " ... a Sa of dates," not mentioning the option for three days. But a Sa of dates is mentioned in most narrations.  

عَنِ النَّبِيِّ ﷺ لاَ تُصَرُّوا الإِبِلَ وَالْغَنَمَ فَمَنِ ابْتَاعَهَا بَعْدُ فَإِنَّهُ بِخَيْرِ النَّظَرَيْنِ بَعْدَ أَنْ يَحْتَلِبَهَا إِنْ شَاءَ أَمْسَكَ وَإِنْ شَاءَ رَدَّهَا وَصَاعَ تَمْرٍ وَيُذْكَرُ عَنْ أَبِي صَالِحٍ وَمُجَاهِدٍ وَالْوَلِيدِ بْنِ رَبَاحٍ وَمُوسَى بْنِ يَسَارٍ عَنْ أَبِي هُرَيْرَةَ عَنِ النَّبِيِّ ﷺ صَاعَ تَمْرٍ وَقَالَ بَعْضُهُمْ عَنِ ابْنِ سِيرِينَ صَاعًا مِنْ طَعَامٍ وَهْوَ بِالْخِيَارِ ثَلاَثًا وَقَالَ بَعْضُهُمْ عَنِ ابْنِ سِيرِينَ صَاعًا مِنْ تَمْرٍ وَلَمْ يَذْكُرْ ثَلاَثًا وَالتَّمْرُ أَكْثَرُ