Albert Barnes Commentary 1 Samuel 15:9

"But Saul and the people spared Agag, and the best of the sheep, and of the oxen, and of the fatlings, and the lambs, and all that was good, and would not utterly destroy them: but everything that was vile and refuse, that they destroyed utterly." — 1 Samuel 15:9 (ASV)

The fatlings - The present Hebrew text cannot be rendered this way. It can only mean “the second best” (compare the margin), that is, sheep at the age when they cut or shed their two teeth—sheep in their prime. It is probable, however, that the reading is corrupt and that “fat or dainty bits” is the true reading.