The wearing of the kippah is not from biblical law, but a rabbinic requirement. The Torah reports that while priests were officiating in the temple they covered their heads with a turban.
"“For Aaron’s sons you shall make tunics; you shall also make sashes for them, and you shall make caps for them, for glory and for beauty. You shall put them on Aaron your brother and on his sons with him; and you shall anoint them and ordain them and consecrate them, that they may serve Me as priests." (Exodus 28:40,41)