English Basic Explanation - Chapter 40
David begins Psalm 40 by praising God for rescuing him from death, and then proceeds to pray that He continue treating him with benevolence and compassion, and save him from those who seek his downfall.
In the first half of this chapter, David reflects philosophically on the salvation he has experienced, urging all people to place their trust only in the Almighty rather than in seemingly powerful human beings (verse 6). He also observes that God does not demand that we bring costly sacrifices to earn His favor and assistance; He asks only that we obey His commandments (verse 7). A person who seeks God's assistance is not required to offer Him sacrifices as a bribe, as one would when seeking the help of another human being; he needs merely to faithfully abide by the Torah's commands. Additionally, David proudly affirms his publicizing God's benevolence, avowing that he has not "withheld" any praises for God's greatness and kindness.
At this point David makes the transition from praising God for helping him in the past, to praying that He help him in the present. He asks that just as he has not "withheld" God's praises, so should God not withhold His compassion and benevolence from him (verse 12). David finds himself surrounded by "innumerable" crises and threats, and he recognizes that his sins render him unworthy of divine assistance (verse 13). He therefore begs for compassion, that God immediately come to his side despite his unworthiness.
In times of hardship and crisis, some people instinctively react by asking questions such as "Why does this always happen to me?" or "Why does God make things so difficult for me?" David, however, responds in the precise opposite fashion. Surrounded by enemies, he turns to the Almighty and declares, "You have been so kind to me in the past; You have so often come to my assistance – I am thus confident that You will rescue me from my current crisis, as well." Rather than bemoaning his current situation, he draws inspiration and encouragement from the past, and humbly prays that God extend His kindness to the present, as well.