Who is David from Dark Night of the Soul and what is their importance?

The Psalms of David are quoted often in St. John's book, particularly to illustrate the way a believer's heart will cry out for God. David was a character in the Bible's Old Testament, who began his life as a shepherd, but ended up a king. Despite his rise in status, however, David made many mistakes in his life and sinned against God in grievous ways.