Muwatta Malik:Zakat:Hadith 620
حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، أَنَّهُ بَلَغَهُ أَنَّ أَبَا بَكْرٍ الصِّدِّيقَ، قَالَ لَوْ مَنَعُونِي عِقَالاً لَجَاهَدْتُهُمْ عَلَيْهِ ‏.‏

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.”