Abdullah bin Ka'b bin Malik al-Ansari (may Allah have mercy on him) said: An army of the Ansar was in Persia with their commander, and it was the practice of Sayyiduna Umar (may Allah be pleased with him) to call armies back after a year. Sayyiduna Umar (may Allah be pleased with him) became neglectful of them. When the appointed time passed, the people of that frontier came back. Sayyiduna Umar (may Allah be pleased with him) was harsh with them and threatened them, even though they were Companions of the Messenger of Allah (peace and blessings be upon him). They said to Sayyiduna Umar (may Allah be pleased with him): You neglected us, and in our case you abandoned the command of the Prophet (peace and blessings be upon him) that "the armies should be brought back in turns."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 17849