It looks like the text is either missing a "which" or an "it". Otherwise the portion after the semicolon is not a complete sentence.
The current text:
How great is the multitude of thy goodness, O Lord, which thou hast hidden for them that fear thee; thou hast wrought for them that trust in thee before the sons of men.
Add a "which"?
How great is the multitude of thy goodness, O Lord, which thou hast hidden for them that fear thee; [which] thou hast wrought for them that trust in thee before the sons of men.
Or an "it"?
How great is the multitude of thy goodness, O Lord, which thou hast hidden for them that fear thee; thou hast wrought [it] for them that trust in thee before the sons of men.
Oh how great is thy goodness, which thou hast laid up for them that fear thee; which thou hast wrought for them that trust in thee before the sons of men!
NETS (an example of "it"):
O how much is the abundance of your kindness, which you hid for those who fear you; you accomplished it for those who hope in you, before the sons of men!
It looks like the text is either missing a "which" or an "it". Otherwise the portion after the semicolon is not a complete sentence.
The current text:
Add a "which"?
Or an "it"?
For comparison.
KJV (an example of "which"):
NETS (an example of "it"):