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.
“thief” = klepto.
“money bag” = glossokomon = a case in which to keep the mouth-pieces of wind instruments. It came to mean a small box made of wood or another rigid material, in which things may be kept and was even used to sometimes designate a casket. Here it means a money-box.
“keeper” (NIV) = “bear” (KJV) = bastazo = to carry. This word can have the double meaning of either to carry or to carry away (steal), much like our English word of “lift.” Judas did both.
This is the one place in the gospels where Judas is shown to be of bad character before his betrayal of Jesus. Note that since Judas was the treasurer for the disciples and Jesus, he must have had some ability in the area of finances. Jesus must have known that Judas was pilfering the money and probably knew he would before they even met. Jesus knew as early as back in (John 6:70-71) that Judas would betray Him. Why, apart from his financial abilities, do you think Jesus put him in charge of the money-box? Barclay thinks that Jesus may have been trying to reclaim him and was treating him with trust instead of suspicion in order that He might win him back.
John 6:70-71 Then Jesus replied, “Have I not chosen you, the Twelve? Yet one of you is a devil!” (He meant Judas, the son of Simon Iscariot, who, though one of the Twelve, was later to betray him.)
Notice that it is through his area of strength that Judas is tempted. Westcott notes that “Temptation commonly comes through that for which we are naturally fitted.” Do you find that true in your own life? Perhaps of greater importance is that opportunity brings temptation?
John presents us with an incredible contrast between Mary, with her wonderful, sacrificial gift, and Judas, with his selfish, greedy desires. Judas has just seen an incredibly beautiful act by Mary and he sees it as a waste. How warped our view of things can be! We can see the beautiful actions of others and view them as just an extravagant waste where Jesus sees them as incredibly lovely. It is what is inside of us that determines how we see things.
In Matthew and Mark, Judas goes right after this to the chief priests and makes his agreement to sell out Jesus (Matt 26:14-16, Mark 14:10-11). The impression given is that Judas has lost one source of income and immediately tries to find another.
Matthew 26:14-16 Then one of the Twelve—the one called Judas Iscariot—went to the chief priests and asked, “What are you willing to give me if I hand him over to you?” So they counted out for him thirty silver coins. From then on Judas watched for an opportunity to hand him over.
Mark 14:10-11 Then Judas Iscariot, one of the Twelve, went to the chief priests to betray Jesus to them. They were delighted to hear this and promised to give him money. So he watched for an opportunity to hand him over.