Question: In Acts 1:18 it says that Judas purchased a field with the ‘reward of iniquity’; but in Matthew 27:5 he gave the 30 pieces of silver back to the priest. How could he buy a field with the money when the Bible says he gave it back?
Answer: Please remember two things about Judas. First, he was a thief. Notice his response to Mary’s anointing of Christ’s feet in John 12:5,6.
"Why was not this ointment sold for three hundred pence, and given to the poor? This he said, not that he cared for the poor; but because HE WAS A THIEF, and had the bag, and bare what was put therein."
Second, he obtained the 30 pieces of silver for betraying Christ, as recorded in Matthew 26:15.
"And said unto them, What will ye give me (Judas), and I will deliver him (Christ) unto you? And they covenanted with him for thirty pieces of silver."
In Acts 1:18 we find:
"Now this man (Judas) purchased a field with the reward of iniquity..."
This field, or "homestead estate," was purchased by Judas with the money he had stolen from the treasury before he died.
The money Judas returned to the priest was used by them after his death to buy a cemetery.
"And the chief priests took the silver pieces...and bought with them (the money) the potter’s field, to bury strangers in." - Matthew 27:6,7
No contradiction at all!