Adam Clarke on Isaiah 14:3

In the day "In that day" - ביום ההוא bayom hahu. The word ההוא hahu is added in two MSS. of Kennicott's, and was in the copies from which the Septuagint and Vulgate translated: εν τῃ ἡμερᾳ εκεινῃ, in die illa, (ᾑ αναπαυσει, MS. Pachom. adding ה), in that day. This is a matter of no great consequence: however, it restores the text to the common form, almost constantly used on such occasions; and is one among many instances of a word apparently lost out of the printed copies.