Then David went over to the other side, and stood on the top of an hill afar off; a great space being between them:

Wesley's Notes

26:13 Afar off - That his person might be out of their reach, and yet his voice might be heard; which in a clear air, and in the silence of the night might be heard at a great distance.

Jamieson-Fausset-Brown Bible Commentary

13-20. Then David . stood on the top of an hill afar off . and cried to the people-(See on [252]Jud 9:7). The extraordinary purity and elasticity of the air in Palestine enable words to be distinctly heard that are addressed by a speaker from the top of one hill to people on that of another, from which it is separated by a deep intervening ravine. Hostile parties can thus speak to each other, while completely beyond the reach of each other's attack. It results from the peculiar features of the country in many of the mountain districts.

Matthew Henry's Concise Commentary

26:13-20 David reasoned seriously and affectionately with Saul. Those who forbid our attendance on God's ordinances, do what they can to estrange us from God, and to make us heathens. We are to reckon that which exposes us to sin the greatest injury that can be done us. If the Lord stirred thee up against me, either in displeasure to me, taking this way to punish me for my sins against him, or in displeasure to thee, if it be the effect of that evil spirit from the Lord which troubles thee; let Him accept an offering from us both. Let us join in seeking peace, and to be reconciled with God by sacrifice.