Jamieson, Fausset and Brown on Amos 5:8

8. the seven stars--literally, the heap or cluster of seven larger stars and others smaller (Job 9:9; 38:31). The former whole passage seems to have been in Amos' mind. He names the stars well known to shepherds (to which class Amos belonged), Orion as the precursor of the tempests which are here threatened, and the Pleiades as ushering in spring.

shadow of death--Hebraism for the densest darkness.

calleth for the waters of the sea--both to send deluges in judgment, and the ordinary rain in mercy (1Ki 18:44).