Our Rabbis said: It is written in Joshua: “As I was with Moses I will be with you” (Joshua 1:5). Joshua should have lived one hundred and twenty years. Why were ten years deducted from his years? When the Holy One blessed be He said to Moses: “Take the vengeance of the children of Israel against the Midianites; then you will be gathered to your people” (Numbers 31:2), even though he was given tidings of death, he did not postpone the matter, but rather, he acted with alacrity – “Moses sent them” (Numbers 31:6).
But Joshua, when he came to wage war with the thirty-one kings, he said: If I kill them immediately, I will die immediately, just as Moses our teacher did. What did he do? He began delaying their war, as it is stated: “For many years, Joshua waged war with all those kings” (Joshua 11:18). The Holy One blessed be He said to him: ‘Since this is what you did, I will deduct ten years from your years.’
Solomon said: “Many are the thoughts in the heart of a man, but it is the counsel of the Lord that will stand” (Proverbs 19:21).