What kinds of conditions are permissible; and what is exempted from the decision

وَالشُّرُوطِ الَّتِي يَتَعَارَفُهَا النَّاسُ بَيْنَهُمْ، وَإِذَا قَالَ مِائَةٌ إِلاَّ وَاحِدَةً أَوْ ثِنْتَيْنِ. وَقَالَ ابْنُ عَوْنٍ عَنِ ابْنِ سِيرِينَ قَالَ رَجُلٌ لِكَرِيِّهِ أَدْخِلْ رِكَابَكَ، فَإِنْ لَمْ أَرْحَلْ مَعَكَ يَوْمَ كَذَا وَكَذَا، فَلَكَ مِائَةُ دِرْهَمٍ. فَلَمْ يَخْرُجْ، فَقَالَ شُرَيْحٌ مَنْ شَرَطَ عَلَى نَفْسِهِ طَائِعًا غَيْرَ مُكْرَهٍ فَهْوَ عَلَيْهِ. وَقَالَ أَيُّوبُ عَنِ ابْنِ سِيرِينَ إِنَّ رَجُلاً بَاعَ طَعَامًا وَقَالَ إِنْ لَمْ آتِكَ الأَرْبِعَاءَ فَلَيْسَ بَيْنِي وَبَيْنَكَ بَيْعٌ. فَلَمْ يَجِئْ، فَقَالَ شُرَيْحٌ لِلْمُشْتَرِي أَنْتَ أَخْلَفْتَ. فَقَضَى عَلَيْهِ.Narrated Ibn Sirin: A man said to a hirer of animals, “Prepare your travelling animals, and if I should not go with you on such and such day, I shall pay you one hundred Dirhams,” but he did not go on that day. Shuraih said, “If anyone puts a condition on himself of his own free will without being under duress, he has to abide by it.” Narrated Ayyub from Ibn Sirin: A man sold foodstuff and the buyer told the seller that if he did not come to him on Wednesday, then the deal would be cancelled (i.e., invalid) and he did not turn up on that day. Shuraih said to the buyer, “You have broken your promise,” and gave the verdict against him.