The Sheep and the Shepherd
Like camels sheep can go long periods of time without water and then drink as much as nine liters. In contrast to goats, which are quite independent, sheep depend on the shepherd to find pasture and water for them. Shepherds also provide shelter, medication and aid in birthing. In sum, they are virtually helpless without the shepherd.
Matthews, V. H., Chavalas, M. W., & Walton, J. H. (2000). The IVP Bible background commentary: Old Testament (electronic ed., Ps 23:2). Downers Grove, IL: InterVarsity Press.