I understand more than the ancients - Hebrew, The old men. It does not refer, as the word "ancients" does with us, to the people of former times, but to aged men. They have treasured up wisdom. They have had the advantage of experience, of study, and of observation. They, therefore, like teachers, become a standard by which we measure our own attainments, as the boy hardly hopes to gain that amount of knowledge which he observes in people who are venerable in years, and who are remarkable for their acquirements. Compare Job 12:12 : "With the ancient is wisdom, and in length of days understanding." Job 32:7 : "I said, Days should speak, and multitude of years should teach wisdom." Compare 1-Kings 4:30-31. Yet the psalmist says that he "had" reached this point, and had even gone beyond what he had once thought he could never attain.
Because I keep thy precepts - It is all the result of an honest endeavor to do right; to observe law; to keep the commands of God. Obedience to the law of God will do more than any mere human teaching to make a man truly wise.

I understand more than the ancients - God had revealed to him more of that hidden wisdom which was in his law than he had done to any of his predecessors. And this was most literally true of David, who spoke more fully about Christ than any who had gone before him; or, indeed, followed after him. His compositions are, I had almost said, a sublime Gospel.

I understand more than the ancients,.... Than those that had lived in ages before him; having clearer light given him, and larger discoveries made unto him, concerning the Messiah, his person and offices particularly, as it was usual for the Lord to do; or than aged men in his own time: for though wisdom, knowledge, and understanding, may be reasonably supposed to be with ancient men; who have had a long experience of things, and have had time and opportunity of making their observations, and of laying up a stock of knowledge; and this may be expected from them, and they may be applied to for it; yet this is not always the case; a younger man, as David was, may be endued with more knowledge and understanding than such; so Elihu; see Job 8:8, Job 32:6. Or, "I have got understanding by the ancients"; so Kimchi; though the other sense seems preferable;
because I keep thy precepts; keep close to the word; attend to the reading of it, and meditation on it; keep it in mind and memory, and observe to do the commands of it; and by that means obtained a good understanding, even a better one than the ancients; especially than they that were without it, or did not carefully attend unto it; see Psalm 111:10.

more than the ancients--Antiquity is no help against stupidity, where it does not accord with God's word [LUTHER] (Job 32:7-9). The Bible is the key of all knowledge, the history of the world, past, present, and to come (Psalm 111:10). He who does the will of God shall know of the doctrine (John 7:17).

Because - The practice of religion is the best way to understand it.