# It will be as a sign and a witness to Yahweh of hosts in the land of Egypt

"The altar will show and prove that Yahweh of hosts is in the land of Egypt" 

# to Yahweh of hosts in the land of Egypt

"that the people in the land of Egypt worship Yahweh of hosts" 

# When they cry

"When the Egyptians cry"

# because of oppressors

"because people are treating them harshly" or "because others are causing them to suffer"

# he will send them a savior and a defender

"Yahweh will send someone to save and defend the Egyptians"