In regards to Psalm 41:9, David wrote this psalm about Ahithophel who was one of David's official counselors (2 Samuel 15:12). As David's friend, Ahithophel defected from the king and joined in Absalom's conspiracy. It is evident that there is messianic connotation given to this verse because Jesus quoted it in speaking of Judas Iscariot in John 13:18. Although David said, mine own familiar friend, in whom I trusted.” Jesus referred to Judas as friend, yet Jesus did not say that He trusted Judas. Why would Jesus trust an unbelieving, unclean devil who He knew would betray Him?
Jesus never trusted the thief, liar, betrayer, son of perdition, the wicked one etc...... all characteristics of the devil himself, not Godly character traits. The thief comes to steal, kill and destroy and that is judas in a nutshell.
John 6:63-65
The words I have spoken to you are spirit and they are life. 64 Yet there are some of you who do not believe."
For Jesus had known from the beginning which of them did not believe and who would betray Him. 65 He went on to say, "This is why I told you that no one can come to me unless the Father has enabled him."
John 6:70-71
Then Jesus replied, "Have I not chosen you, the Twelve?
Yet one of you is a devil!" 71 (He meant Judas, the son of Simon Iscariot, who, though one of the Twelve, was later to betray Him.)
John 12:4-6
But one of his disciples, Judas Iscariot, who was later to betray Him, objected, 5 "Why wasn't this perfume sold and the money given to the poor? It was worth a year's wages." 6 He did not say this because he cared about the poor but because
he was a thief; as keeper of the money bag, he used to help himself to what was put into it.
John 13:10-11
10 Jesus answered, "A person who has had a bath needs only to wash his feet; his whole body is clean. And you are clean, though not every one of you." 11 For He knew who was going
to betray Him, and that was why He said not every one was clean.
John 17:12
12 While I was with them, I protected them and kept them safe by that name you gave me. None has been lost except
the one doomed to destruction so that Scripture would be fulfilled.
Matt 26:23-25
23 Jesus replied, "The one who has dipped his hand into the bowl with me will betray me. 24 The Son of Man will go just as it is written about him. But woe to that man who betrays the Son of Man!
It would be better for him if he had not been born."
25 Then Judas, the one who would betray him, said, "Surely not I, Rabbi?"
Jesus answered, "Yes, it is you."
Acts 1:16-19
16 and said, "Brothers, the Scripture had to be fulfilled which the Holy Spirit spoke long ago through the mouth of David concerning
Judas, who served as guide for those who arrested Jesus— 17 he was one of our number and shared in this ministry."
18 (With the reward he got for his wickedness, Judas bought a field; there he fell headlong, his body burst open and all his intestines spilled out. 19 Everyone in Jerusalem heard about this, so they called that field in their language Akeldama, that is, Field of Blood.)
Acts 1:24-26
Show us which of these two you have chosen 25 to take over this apostolic ministry,
which Judas left to go where he belongs." 26 Then they cast lots, and the lot fell to Matthias; so he was added to the eleven apostles.
Ps 109:4-8
In return for my friendship they accuse me,
but I am a man of prayer.
5 They repay me evil for good,
and hatred for my friendship.
6 Appoint an evil man to oppose him;
let an accuser stand at his right hand.
7 When he is tried,
let him be found guilty,
and may his prayers condemn him.
8 May his days be few;
may another take his place of leadership.