حَدَّثَنَا سُلَيْمَانُ بْنُ دَاوُدَ، أَخْبَرَنَا ابْنُ وَهْبٍ، أَخْبَرَنِي عُثْمَانُ بْنُ الْحَكَمِ، عَنْ يَحْيَى بْنِ سَعِيدٍ، أَنَّهُ قَالَ لاَ جَائِحَةَ فِيمَا أُصِيبَ دُونَ ثُلُثِ رَأْسِ الْمَالِ - قَالَ يَحْيَى - وَذَلِكَ فِي سُنَّةِ الْمُسْلِمِينَ ‏.‏

Yahya b. Sa'id said: Blight is not effective when less than one-third of goods are damaged. Yayha said: That has been the established practice of Muslims. Translation Not Available

Book Ref: Sunan Abi Dawud Book 24 Hadith 3472
Web Ref:  Sunan Abi Dawud Book 23 Hadith 3465