Agur asks God for two things:
Help to avoid lying (compare Proverbs 6:16–19; 14:5, 25; 25:18; 26:18–19)
To not have too much or too little
Being rich (Proverbs 3:9–10, 15–16; 10:15, 22) or poor (3:27; 11:24; 28:27; 29:7, 14) is not sinful, but Agur wisely wants to avoid the problems of both.