'Pairs' in the Bible

From all the clean animals you must take for yourself {seven pairs}, a male and its mate. And from the animals that [are] not clean [you must take] two, a male and its mate,

as well as from the birds of heaven {seven pairs}, male and female, {to keep their kind alive} on the face of the earth.

and he said, "When you help the Hebrews give birth, you will look upon the pairs of testicles; if he [is] a son, you will put him to death, and if she [is] a daughter, she will live."

So he went from there and found Elisha son of Shaphat while he [was] plowing [with] twelve pairs of oxen before him. When he and the twelve passed Elijah, he threw his cloak on him.

Then his livestock came to be seven thousand sheep and goats and three thousand camels and five hundred pairs of oxen and five hundred female donkeys, and he had very many slaves, and that man was greater than all the people of the east.