Charles H. Spurgeon on Psalms 78:17

They sinned yet more. Their sin was not murmuring only, sinful as that is, but uncontrolled desire. And for what was that desire? It was for meat. They had grown so weary of the bread of heaven which God so mercifully provided; and they wanted something in addition —something, too, which was not absolutely necessary to their existence. When they murmured for water at Massah, they murmured for something needful. Their sin then was in murmuring, instead of praying. But here they lusted for something unnecessary, and this was an aggravation of their sin. And thus the psalmist, evidently comparing this sin with the murmuring at Massah, says, "They sinned yet more against him." George Wagner, in "The Wanderings of the Children of Israel."