Sunan Abi Dawud, Hadith 1611

Abd’ Allah(b. 'Umar) said “The people then began to pay half a sa’ of wheat later on. The narrator said : 'Abd Allah (b. Umar) use to pay dried dates as sadaqah one year the people of Medina lacked dried dates, hence he paid barley.

حَدَّثَنَا مُسَدَّدٌ، وَسُلَيْمَانُ بْنُ دَاوُدَ الْعَتَكِيُّ، قَالاَ حَدَّثَنَا حَمَّادٌ، عَنْ أَيُّوبَ، عَنْ نَافِعٍ، قَالَ قَالَ عَبْدُ اللَّهِ فَعَدَلَ النَّاسُ بَعْدُ نِصْفَ صَاعٍ مِنْ بُرٍّ ‏.‏ قَالَ وَكَانَ عَبْدُ اللَّهِ يُعْطِي التَّمْرَ فَأَعْوَزَ أَهْلَ الْمَدِينَةِ التَّمْرُ عَامًا فَأَعْطَى الشَّعِيرَ ‏.‏

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also referenced under: Hadith 1615 (DarusSalam)