The Stag, the Wolf and the Sheep

A Stag asked a Sheep to lend him a measure of wheat, and said that the Wolf would be his surety. The Sheep, fearing some fraud was intended, excused herself, saying: "The Wolf is accustomed to seize what he wants, and to run off, and you, too, can quickly out-strip me in your rapid flight. How then shall I be able to find you when the day of payment comes?"

Two blacks do not make one white.