# Oh, that the salvation of Israel would come

"I hope that the salvation of Israel will come" or "I pray that the salvation of will come" 

# the salvation of Israel would come from Zion

"the savior of Israel would come from Zion" or "God would come from Zion and save Israel" 

# When God brings back his people from the captivity

"When God saves his captive people"

# Jacob

Here "Jacob" refers to the descendants of Jacob, the Israelites.