David referred to God the mistreatment of his enemies. Psalm 41:5-9 says, "My enemies speak evil against me:/When will he die and his name perish?/And if he comes to see me, he speaks falsehood./His heart gathers iniquity to itself;/When he goes out, he speaks it./All who hate me whisper together against me;/Against me they devise my misfortune./Some evil illness, they say, is cast upon him;/And when he lies down, he will not rise again./Even my familiar friend, in whom I trusted,/Who ate my bread, has lifted his heel against me." David told God in detail concerning how his enemies had mistreated him.
David's enemies pretended that they were his friends. This is why they could come to see him and speak falsehood. Today many people are like this. They are so nice to a person in a way of pretense when they are with him, but when they leave his presence, they speak what they really feel about him. This is falsehood. David's enemies even said that some evil illness was cast upon him.
In the midst of these mixed expressions of David's sentiment, David spoke a word which became a prophecy concerning Judas Iscariot, who betrayed the Lord Jesus. Verse 9 says, "Even my familiar friend, in whom I trusted,/Who ate my bread, has lifted his heel against me." This word was quoted by the Lord in John 13:18 in reference to Judas.
David expected his enemies to be desolate and put to shame (Psa. 40:14-15; 41:10-11).
In such mixed expressions of his sentiment, David prophesied concerning Christ. The prophecy in Psalm 40:6-8 is a great prophecy concerning Christ, and the prophecy in Psalm 41:9 is a small prophecy concerning Judas betraying Christ.