At that same time the leading priests and elders were meeting at the residence of Caiaphas, the high priest, plotting how to capture Jesus secretly and kill him. But not during the Passover celebration, they agreed, or the people may riot. Matthew 26:3-5
Then Judas Iscariot, one of the twelve disciples, went to the leading priests and asked, “How much will you pay me to betray Jesus to you?” And they gave him thirty pieces of silver. From that time on, Judas began looking for an opportunity to betray Jesus.