Charles Ellicott Commentary Isaiah 21:16

"For thus hath the Lord said unto me, Within a year, according to the years of a hireling, all the glory of Kedar shall fail;" — Isaiah 21:16 (ASV)

According to the years of an hireling ... The prophet uses, as in Isaiah 16:14, the formula which expressed the most precise measurement, and so gives a test as to his forecast of the future.

And all the glory of Kedar shall fail. —Kedar is used, as in Psalms 120:5, Song of Solomon 1:5, generically for the nomadic tribes of Arabia, including Dedan.