Sayyiduna al-Sa'ib bin Yazid (may Allah be pleased with him) says: In the year of famine, the Muslims suffered severe hunger. One day Sayyiduna Umar (may Allah be pleased with him) was riding his mount, and he saw a grain of barley in its dung. He said: By Allah! I will not ride it until the condition of the people improves.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17911