Jesus was filled with the Holy Spirit, because he had just been Baptized by John the Baptist, who was filled with the Holy Spirit while in his mothers womb. Almost all the people John Baptized, in the wilderness by the Jordon, were filled with the Holy Spirit. All had taken the Vow of the Nazarite for a short period of time. Being cleansed of ones remaining sins, completed the Vow. One is then bid to go into the desert wilderness, and reject all temptations. Having done that, God comes and fills you with the His Holy Spirit. He makes you One with Him. You are His Son, now! God had many sons who would help Him bring about the Great Atonement, when God frees Israel from the Roman Slave Masters.