Muwatta Malik, Book 17, Hadith 31 (USC-MSA)

Yahya related to me from Malik that he had heard that Abu Bakr as-Siddiq said, "If they withhold even a hobbling cord I will fight them over it."

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ أَبَا بَكْرٍ الصِّدِّيقَ، قَالَ لَوْ مَنَعُونِي عِقَالاً لَجَاهَدْتُهُمْ عَلَيْهِ ‏.‏

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also referenced under: Book 17, Hadith 608 (In-Book)