1 Samuel 17:29

If you don't mind, however, let us refer to a theme in our preaching earlier, so that by bringing the whole story to mind we may learn that nothing is stronger than the person protected by help from on high, and nothing is more vulnerable than the person deprived of this help, surrounded though he may be with countless armies. So this man David, quite young though he was and living in his father's house on account of his immaturity, heard the call of destiny for his virtue to become conspicuous; he was urged by his father to observe his brothers; he obeyed and was sent off to them. So, after coming on the scene to observe them, he saw the battle line drawn against the foreigner Goliath and the whole people of Saul's company withdrawing in fright and the king himself placed in particular danger. For a while he was happy to be an onlooker and went to see the strange and unusual sight of one person pitted against so many thousands. But his brothers could not tolerate the manliness of his bearing; they were moved to hatred and said to him, "Have you come for no other reason than to see the war." You haven't really come to observe us.Notice, however, his good sense and great restraint. Instead of saying anything rash to them, anything harsh, he extinguished the flame of their hatred; he mollified their hatred by saying, "Isn't it only a word?" I mean, surely you haven't observed me taking position in the ranks? I simply wanted to watch and find out the source of this man's extraordinary frenzy. "After all, who is this foreigner who reproaches the ranks of the living God?" Then, on hearing the man's awful arrogance and the unspeakable cowardice of those who had gone with Saul, he said, "What will be given to the man who cuts off his head?" He showed great boldness of spirit through these words and caused amazement in every one. […]

This conquest of his own passion was in some respects more honourable than his conquest of Goliath. He that hath rule over his own spirit is better than the mighty. It was no time for David to quarrel with his brother when the Philistines were upon them.

Is this giant invincible? Is our God unable to oppose him, and subdue him? However David is not deterred from his undertaking, by the hard words of Eliab.

And David said, what have I now done?.... That is criminal and blameworthy; as if he should say, I have only expressed an indignation against this uncircumcised Philistine, and a concern for the glory of God, and the honour of the people of Israel: is there not a cause? either for his coming to the camp, being sent by his father; or of his expressing himself with indignation at the Philistine's defiance of the armies of Israel.

Is there not a cause? - הלוא דבר הוא halo dabar hu. I believe the meaning is what several of the versions express: I have spoken but a word. And should a man be made an offender for a word?