Sunan Abi Dawud 2960

Narrated 'Abd Allah b. Ka'b b. Malik al-Ansari:An expedition of the Ansar was operating in Persia with their leader. 'Umar used to send expeditions by turns every year, but he neglected them. When the expired, the people of expedition appointed on the frontier came back. He ('Umar) took serious action against them and threatened them, though they were the Companions of the Messenger of Allah (ﷺ). They said: 'Umar you neglected us, and abandoned the practice for which the Messenger of Allah (ﷺ) commanded to send the detachments by turns