Strengthen your faith in God's word

Matt. 27:5 Judas cast the silver in the temple.

Acts 1:18 He brought a field with this money

Judas could not have done both.

Judas had indirectly purchased the field with blood money (the 30 pieces of silver given to him to betray Jesus Christ). When he threw the blood money in front of the chief priests, they used it to buy the field called Aceldama (the field of blood) or "the potter's field."

Matt. 27:5. And he cast down the pieces of silver in the temple, and departed, and went and hanged himself.
6. And the chief priests took the silver pieces, and said, It is not lawful for to put them into the treasury, because it is the price of blood.
7. And they took counsel, and bought with them the potter's field, to bury strangers in.
8. Wherefore that field was called, The field of blood, unto this day.

Apparently, when Judas threw the money in the temple, he went to hang himself, but his attempt failed and "falling headlong, he burst asunder in the midst, and all his bowels gushed out." Judas had, in a figurative way, purchased the field with "the reward of iniquity," his life. This makes perfect sense b/c the consequence or "reward" of sin is death. When Judas died the priests bought the potter's field, the very same field that Judas committed suicide in. The people later renamed it Aceldama or "the field of blood."

Acts 1:19. And it was known unto all the dwellers at Jerusalem; insomuch as that field is called in their proper tongue, Aceldama, that is to say, The field of blood.

This is a fitting name, since this piece of land, "the field of blood," is purchased with blood money. Also, this event is a fitting picture of what Jesus Christ did for us. The field can be seen as a type of the world where the good seed of the Word of God is sown. "The field is the world" (Matt. 13:38) and Jesus Christ, as the Man, searches for "treasure hid in a field...selleth all that he hath, and buyeth that field" (Matt. 13:44). The price for purchasing this field (the world) is Jesus Christ's very life, His very blood, which is shed so that we, dead in our sins and hidden in the world, might be "purchased with his own blood." (Acts 20:28)

Conclusion: The field Aceldama was purchased directly by the priests and indirectly by Judas, with the price of Jesus Christ's shed blood (the blood money). The field had literally been purchased by Jesus Christ's shed blood and spiritually represents what Jesus Christ did at the cross for the whole world.

A complete reading of Matt. 27:3-7 will make this clear.
Notice that Matt. 27:3 has Judas returning the money to the priests. When they refused it(v.4), he simply cast the money down in the temple(v.5). Even then, the priests would not return the money to the temple treasury "because it is the price of blood."(v.6). So, they took the money, which still belonged to Judas, and used it to buy the field(v.7).

Peter simply employs a common figure of speech in Acts 1:18, when he speaks of Judas having purchased that which was purchased with his money.