water for money - The Jews were compelled to pay the enemy for the water of their own cisterns after the overthrow of Jerusalem; or rather, it refers to their sojourn in Babylon; they had to pay tax for access to the rivers and fountains. Thus, “our” means the water which we need, the commonest necessary of life.
our wood - In Judea each one could get wood without pay; in Babylon, “our wood,” the wood we need, must be paid for.