Then Jesus’ [half-] brothers said to Him, “You should leave here and go to Judea so your disciples [there] can see the [supernatural] deeds you are performing.
While Jesus was still speaking to the large crowds, His mother and [half-] brothers were standing outside [of the large house. See 13:1] wanting to speak to Him.
But Peter [responded by] standing up with the eleven [other] apostles and, lifting up his voice, began to speak. He said, “People of Judea and all who live in Jerusalem, listen to what I am saying so you will understand this situation.
Then Jesus’ mother and [half-] brothers came and stood outside [i.e., of a large house. See Matt. 12:46-13:1]. They sent a message to Him, asking Him to come out to them.
When His relatives [or friends] heard about this [i.e., all that He was doing], they went out to take custody of Him [for safety reasons (?)], for people were saying, “He has lost his mind.”
Upon [hearing] this, many of Jesus’ disciples turned back and refused to accompany Him anymore. [Note: They deserted Jesus physically as well as spiritually].