Judas Iscariot
There are several explanations as to why Judas betrayed Jesus. In the earliest account, in the Gospel of Mark, when he goes to the chief priests to betray Jesus, he is offered money as a reward, but it is not clear that money is his motivation. In the Gospel of Matthew account, on the other hand, he asks what they will pay him for handing Jesus over. In the Gospel of Luke and the Gospel of John, the devil enters into Judas, causing him to offer to betray Jesus. The Gospel of John account has Judas complaining that money has been spent on expensive perfumes to anoint Jesus which could have been spent on the poor, but adds that he was the keeper of the apostles' purse and used to steal from it.
Judaism's view of Jesus
Maimonides lamented the pains that Jews felt as a result of new faiths that attempted to supplant Judaism, specifically Christianity and Islam. Referring to Jesus, he wrote:
Even Jesus the Nazarene who imagined that he would be Messiah and was killed by the court, was interpreted as prophesied by Daniel. So that it was said, "And the members of the outlaws of your nation would be carried to make a (prophetic) vision stand. And they stumbled" (Daniel 11.14). Because, is there a greater stumbling-block than this one? So that all of the prophets spoke that the Messiah redeems Israel, and saves them, and gathers their banished ones, and strengthens their commandments. And this one caused (nations) to destroy Israel by sword, and to scatter their remnant, and to humiliate them, and to exchange the Torah, and to make the majority of the world err to serve a divinity besides God.