Hastings' Dictionary of the Bible (1898)
COW, Isa 7:21. In this remark Cormorant. ) Crane. ) able prophecy the event foretold is that the face of the land of Judah should be so completely changed, and the inhabitants so greatly reduced in number, that, with only a single young cow and two sheep, a family should be supplied with an abundance of milk and butter, and vineyards which before commanded a high rent should be overgrown with briers and thorns. By the Levitical law, Lev 22:28, a cow and her calf were not to be killed on the same day. A similar precept is found in Ex 23:19, and another in Deut 22:6-7.
Whether they were designed to prevent inhumanity or referred to some heathen custom is uncertain. The cow is esteemed holy by the Hindoos.