'Appear Before Me' in the Bible

Thou shalt keep the feast of unleavened bread: (thou shalt eat unleavened bread seven days, as I commanded thee, in the time appointed of the month Abib; for in it thou camest out from Egypt: and none shall appear before me empty:)

But the firstling of an ass thou shalt redeem with a lamb: and if thou shalt not redeem him, then shalt thou break his neck. All the first-born of thy sons thou shalt redeem. And none shall appear before me empty.

When ye come to appear before me, who hath required this at your hand, to tread my courts?