According to Luke 4:1-2, Jesus, after his water baptism at the Jordan river, was full of the Spirit and was led by the Spirit to a 40-day fast:
Now Jesus, full of the Holy Spirit, returned from the Jordan and was led around by the Spirit in the wilderness 2 for forty days, being tempted by the devil. And He ate nothing during those days, and when they had ended, He was hungry. [Luke 4:1-2 NASB]
The details of the 40-day fast are well known by everybody and can be found in verses 3-13. However, verse 14 says something interesting:
14 And Jesus returned to Galilee in the power of the Spirit, and news about Him spread through all the surrounding region.
In other words, we have the following sequence of events: 1) water baptism, 2) full of the Spirit, 3) 40-day fast, 4) return in the power of the Spirit, 5) news about Jesus spreading everywhere.
Question: is there a causal relationship between points 3 and 4? Was the 40-day fast a necessary condition for Jesus to unleash greater levels of power in the Spirit in order to carry out his powerful ministry?