Musar zu Tehillim 131:76

We have an allusion to this in Psalms 131. David testifies that though he had certainly attained a measure of understanding about the ways of G–d, this had not been a cause for him to become proud or haughty. In this Psalm the words לא גבה לבי allude to the שלימות הגוף, whereas the following words ולא רמו עיני allude to the שלימות הממון, seeing that it is the eye which is usually the cause of greed for money. The last words ולא הלכתי בגדולות refer to the שלימות הנפש. It means that David did not seek out merits which were beyond his ability to achieve, and when he was granted them he did not boast about such achievements. When our sages report that any halachic ruling made by David was always accepted as final this may have been the reward for his humility.