Kiss his lips - Shall treat him with affection and respect.
Albert Barnes
Notes on the Whole Bible
Better, He shall kiss lips that giveth a right answer, i. e., he shall gain the hearts of men as much as by all outward signs of sympathy and favor. Compare 2 Samuel 15:1-6.
Matthew Henry
Concise Bible Commentary
The wisdom God giveth, renders a man fit for his station. Every one who finds the benefit of the right answer, will be attached to him that gave it. 27. We must prefer necessaries before conveniences, and not go in debt. 28,29. There are three defaults in a witness pointed out.
SDA Bible Commentary (limited)
Volume 1-7
26. Kiss his lips. This verse reads literally, “He will kiss the lips who returns a right answer.” When a king, ruler, or judge speaks just words they are as pleasant to right-thinking people as a kiss.