The scripture is (Psalms 41:9) in which David is referring to Ahithophel, his former advisor who betrayed him to follow Absolom. Note the similarities between Ahithophel and Judas (2 Samuel 15:12, 16:23, 17:1-23). What do you think Judas will reap as his reward for betraying Jesus? (Heb 10:29)

Psalms 41:9  Even my close friend, whom I trusted, he who shared my bread, has lifted up his heel against me.

2 Samuel 15:12  While Absalom was offering sacrifices, he also sent for Ahithophel the Gilonite, David’s counsellor, to come from Giloh, his home town. And so the conspiracy gained strength, and Absalom’s following kept on increasing.

2 Samuel 16:23  Now in those days the advice Ahithophel gave was like that of one who enquires of God. That was how both David and Absalom regarded all of Ahithophel’s advice.

2 Samuel 17:1-23  Ahithophel said to Absalom, “I would choose twelve thousand men and set out tonight in pursuit of David.  I would attack him while he is weary and weak. I would strike him with terror, and then all the people with him will flee. I would strike down only the king  and bring all the people back to you. The death of the man you seek will mean the return of all; all the people will be unharmed.”  This plan seemed good to Absalom and to all the elders of Israel.  But Absalom said, “Summon also Hushai the Arkite, so that we can hear what he has to say.”  When Hushai came to him, Absalom said, “Ahithophel has given this advice. Should we do what he says? If not, give us your opinion.”  Hushai replied to Absalom, “The advice Ahithophel has given is not good this time.  You know your father and his men; they are fighters, and as fierce as a wild bear robbed of her cubs. Besides, your father is an experienced fighter; he will not spend the night with the troops.  Even now, he is hidden in a cave or some other place. If he should attack your troops first, whoever hears about it will say, ‘There has been a slaughter among the troops who follow Absalom.’  Then even the bravest soldier, whose heart is like the heart of a lion, will melt with fear, for all Israel knows that your father is a fighter and that those with him are brave.  “So I advise you: Let all Israel, from Dan to Beersheba—as numerous as the sand on the seashore—be gathered to you, with you yourself leading them into battle.  Then we will attack him wherever he may be found, and we will fall on him as dew settles on the ground. Neither he nor any of his men will be left alive.  If he withdraws into a city, then all Israel will bring ropes to that city, and we will drag it down to the valley until not even a piece of it can be found.”  Absalom and all the men of Israel said, “The advice of Hushai the Arkite is better than that of Ahithophel.” For the LORD had determined to frustrate the good advice of Ahithophel in order to bring disaster on Absalom.  Hushai told Zadok and Abiathar, the priests, “Ahithophel has advised Absalom and the elders of Israel to do such and such, but I have advised them to do so and so.  Now send a message immediately and tell David, ‘Do not spend the night at the fords in the desert; cross over without fail, or the king and all the people with him will be swallowed up.’”  Jonathan and Ahimaaz were staying at En Rogel. A servant girl was to go and inform them, and they were to go and tell King David, for they could not risk being seen entering the city.  But a young man saw them and told Absalom. So the two of them left quickly and went to the house of a man in Bahurim. He had a well in his courtyard, and they climbed down into it.  His wife took a covering and spread it out over the opening of the well and scattered grain over it. No-one knew anything about it.  When Absalom’s men came to the woman at the house, they asked, “Where are Ahimaaz and Jonathan?” The woman answered them, “They crossed over the brook.” The men searched but found no-one, so they returned to Jerusalem.  After the men had gone, the two climbed out of the well and went to inform King David. They said to him, “Set out and cross the river at once; Ahithophel has advised such and such against you.”  So David and all the people with him set out and crossed the Jordan. By daybreak, no-one was left who had not crossed the Jordan.
When Ahithophel saw that his advice had not been followed, he saddled his donkey and set out for his house in his home town. He put his house in order and then hanged himself. So he died and was buried in his father’s tomb.

Hebrews 10:29  How much more severely do you think a man deserves to be punished who has trampled the Son of God under foot, who has treated as an unholy thing the blood of the covenant that sanctified him, and who has insulted the Spirit of grace?

The eating of bread together signified close fellowship and loyalty (2 Samuel 9:7, 13, 1 Kings 18:19). The action of Judas is all the more heinous because he is not betryaing an aquaintance, but a close friend (Psalms 41:9, 55:12-14).

2 Samuel 9:7  “Don’t be afraid,” David said to him, “for I will surely show you kindness for the sake of your father Jonathan. I will restore to you all the land that belonged to your grandfather Saul, and you will always eat at my table.”

2 Samuel 9:13  And Mephibosheth lived in Jerusalem, because he always ate at the king’s table, and he was crippled in both feet.

1 Kings 18:19  Now summon the people from all over Israel to meet me on Mount Carmel. And bring the four hundred and fifty prophets of Baal and the four hundred prophets of Asherah, who eat at Jezebel’s table.”

Psalms 41:9  Even my close friend, whom I trusted, he who shared my bread, has lifted up his heel against me.

Psalms 55:12-14  If an enemy were insulting me, I could endure it; if a foe were raising himself against me, I could hide from him.  But it is you, a man like myself, my companion, my close friend,  with whom I once enjoyed sweet fellowship as we walked with the throng at the house of God.

The phrase “lifted up his heel” literally means “has magnified his heel” or “has made great his heel” against me. It is a metaphor that comes from a horse lifting its hoof in preperation for kicking and it indicates cruelty or brutal violence.

“But this is to fulfill the scripture” = does not mean “so that scripture will be fulfilled,” but “by which scripture will be fulfilled.” God has already seen and knows what action Judas will take, but Judas must make those decisions all by himself, and bear the responsibility thereof. Even as terrible as this tragedy is going to be, it is going to be used by God to accomplish His ends. If God can use this most heinous of crimes to accomplish so much good, what can He do with the bad things that happen to you?

Romans 8:28  And we know that in all things God works for the good of those who love him, who have been called according to his purpose.