Jamieson, Fausset and Brown on Isaiah 30:6

6. burden--the prophecy as to, &c. [Maurer]; so the Septuagint, the fresh inscription here marks emphatically the prediction that follows. Or, rather, Isaiah sees in vision, the ambassador's beasts burdened with rich presents travelling southwards (namely, to Egypt, Da 11:5, 6), and exclaims, Oh, the burden of treasure on the beasts! &c. (Ho 8:9; 12:1).

land of trouble--the desert between Palestine and Egypt, destitute of water and abounding in dangerous animals (De 8:15; Jr 2:6).

flying serpent--(Is 14:29), a species which springs like a dart from trees, on its prey.

will carry--rather, present, "carry," namely, as presents to Egypt (1Ki 15:19).

young asses--rather, "full-grown asses" [Maurer].