'Pair' in the Bible

Thus saith Jehovah: For three transgressions of Israel, yea, for four, I will not turn away the punishment thereof; because they have sold the righteous for silver, and the needy for a pair of shoes-

that we may buy the poor for silver, and the needy for a pair of shoes, and sell the refuse of the wheat?

and to offer a sacrifice according to that which is said in the law of the Lord, A pair of turtledoves, or two young pigeons.