Thou, O God, didst send a plentiful rain, whereby thou didst confirm thine inheritance, when it was weary. Didst send a plentiful rain - גשם נדבות geshem nedaboth, a shower of liberality. I believe this to refer to the manna by which God refreshed and preserved alive the weary and hungry Israelites.
Related Commentaries of Psalms 68:9
Psalms 68:9
9 Thou, O God, didst sendd a plentiful rain, whereby thou didst confirm thine inheritance, when it was weary.