John Calvin Commentary Psalms 39:3

"My heart was hot within me; While I was musing the fire burned: [Then] spake I with my tongue:" — Psalms 39:3 (ASV)

My heart became hot within me. He now illustrates the greatness of his grief by introducing a simile, telling us that his sorrow, being internally suppressed, became all the more inflamed, until the ardent passion of his soul continued to increase in strength. From this we can learn the very profitable lesson that the more strenuously anyone sets themselves to obey God and uses all their efforts to practice patience, the more vigorously they are assailed by temptation: for Satan, while he is not so troublesome to the indifferent and careless and seldom goes near them, displays all his forces in hostile array against that individual.

Therefore, if at any time we feel ardent emotions struggling and causing a commotion in our hearts, we should remember this conflict of David, so that our courage may not fail us, or at least so that our weakness may not drive us headlong into despair. The dry and hot vapors that the sun causes to rise in summer, if nothing in the atmosphere obstructed their progress, would rise into the air without commotion; but when intervening clouds prevent their free ascent, a conflict arises from which thunder is produced.

It is similar for the godly who desire to lift up their hearts to God. If they were to resign themselves to the vain imaginations that arise in their minds, they might enjoy a kind of unrestrained liberty to indulge in every fancy; but because they endeavor to resist their influence and seek to devote themselves to God, obstructions that arise from the opposition of the flesh begin to trouble them.

Therefore, whenever the flesh puts forth its efforts and kindles a fire in our hearts, let us recognize that we are being tested by the same kind of temptation that caused so much pain and trouble for David. At the end of the verse, he acknowledges that the severity of the affliction with which he was visited had at last overcome him, and that he allowed foolish and ill-advised words to pass from his lips.

In his own person, he sets before us a mirror of human weakness, so that, being warned by the danger to which we are exposed, we may learn early to seek protection under the shadow of God’s wings. When he says that he spoke with his tongue, it is not a superfluous mode of expression but a true and fuller confession of his sin, in that he had not only given way to sinful murmuring, but had even uttered loud complaints.