Jesus began to spread Christianity in the areas of Galilee, Samaria, and Judea in the 1st century AD. These were the lands that were inhabited by the Jews and the region that Jesus was born in.
Galilee
Galilee was the region of northern Israel in which Jesus spent much of his ministry. He preached throughout the region, and many of Jesus’s parables were set in Galilee. Jesus also performed many miracles in the region, which helped to spread Christianity.
Samaria
Samaria was the region between Galilee and Judea. It was the home of the Samaritans, a Jewish sect who were considered to be heretics by many Jews. Jesus travelled through Samaria and preached to the Samaritans. This helped to spread Christianity to a wider audience.
Judea
Judea was the region in the south of Israel. Jesus visited Jerusalem, the capital of Judea, multiple times. He preached in the city and performed miracles, which helped to spread Christianity. He also visited the surrounding towns and villages, which spread the message of Christianity even further.