Luke lets us know that the crowds were searching high and low for Jesus (Luke 4:42b). The crowds found him, but not before his disciples did. We find in Mark 1:36–37 that his disciples knew this and had set out to find Jesus before the crowds could get to him: “Simon and his companions looked high and low (κατεδίωξεν) for him; and they found him, and said to him, ‘Everyone is looking for you.’”
Here's just a quick little tangent: M. Eugene Boring notes this word, which I translated above as "looked high and low," could have “a slightly hostile tone, ‘tracked him down,’ but need not” (Mark: A Commentary, 68). He opts for the translation "pursue," he says, to retain ambiguity in English. The word is different than other “search” lexemes (e.g., ζητέω [Matt. 2:13]; ἐραυνάω [John 7:52; Acts 21:4]). Peter loves these prefixed prepositions. They add color and speed to his narrative.
Why were the crowds looking for Jesus? Luke clearly states that they “tried to keep [Jesus] from going away from them” (Luke 4:42c). The crowds want to keep Jesus all to themselves, similar to how three disciples were content to build tabernacles once they had witnessed Jesus’ transfiguration. The crowds here do not understand who Jesus fully is and what he must do. They end up acting selfishly and are content with all that they have seen thus far. In other words, if Jesus would just stay in Capernaum, that would be alright with all of them. No reason for him to go city to city. No reason to carry this message of repentance anywhere else. They are fine as long as Jesus heals all the sick, protects them from demons, and keeps teaching in their synagogue. And their selfishness is a threat to Jesus’ ministry of announcing the kingdom. Joel B. Green writes, “They do not understand his mission and, therefore, like the devil before them (4:1–13), function as a force set on waylaying Jesus from his vocation.”
There are basically two possible explanations for why Jesus paused at this moment in his ministry to pray for an extended period of time. Whether it is one or both is up for discussion. The first deals with the intensity of the evening. People were bring all sorts of sick, handicapped, and demon-possessed people to Jesus. And while some scholars might question the notion that Jesus needed to regain his strength, that does seem like a factor. M. Eugene Boring, for example, shrugs off the idea that Jesus needed strength after a long night’s ministry: “There is no indication that he is praying for power to do more miracles, as though his spiritual batteries, drained by the intensity of the preceding day, needed recharging” (Boring, Mark: A Commentary, 68). Jesus performed all of his miracles through the power of the Holy Spirit. That power was really limitless. But Jesus was also entirely human, not just divine. He took on human flesh at the incarnation and so every human limitation, such as stamina, was as much a part of his ministry as it was for the disciples. Jesus understood that his ministry over the next two-and-a-half years would be marked more by nights like the one he just concluded. Unless he carved out time in his schedule for rest, he would have no rest. And the lack of rest could be as detrimental to his ministry as forty days in the wilderness being tempted by the evil one. That period of temptation was so taxing on Jesus that angels were sent to “minister to him.” And even though the authors of the Gospels do not specifically mention that Jesus was praying, neither before nor after the temptation, we can assume he was since it specifically mentions that he “ate nothing during those days,” an indication that Jesus was fasting; fasting and prayer go hand in hand in other places in the Gospels (e.g. Luke 2:37; Luke 5:33; Matt. 17:21). He needed strength before his encounter with Satan, and he needed to regain his strength after as well. Closely connected to this is the sub-reason that Jesus was providing an example for his disciples, one they would need to follow as they participated in his ministry, both leading up to his crucifixion and once Jesus departed this world and left them to work in his stead. The need for strength is connected to prayer in places like Mark 14:38, where Jesus tells his disciples: “Keep watching and praying that you may not come into temptation; the spirit is willing, but the flesh is weak.”
The second possible explanation for this extended period of time in prayer deals with what lies ahead in his ministry. James R. Edwards points out the following concerning Jesus’ prayer in the Gospel of Mark: “There are three references to Jesus praying in Mark (1:35; 6:46; 14:32–39); in each he is alone and facing critical junctures in his ministry” (James R. Edwards, The Gospel According to Mark, The Pillar New Testament Commentary , 281). He adds the following observations:
"Each prayer is at night and in a lonely place, each finds the disciples removed from him and failing to understand his mission, and in each Jesus faces a formative decision or crisis. Following the feeding of the five thousand, Jesus reaffirms by prayer his calling to express his divine Sonship as a servant rather than as a freedom fighter against Rome." (Edwards, The Gospel According to Mark, 197)What were these critical junctures? In Mark 14 it was the impending crucifixion. In Mark 6 Jesus’ ministry had just taken a drastic turn, marked by Jesus’ switch from teaching openly when in public to his use of parables. And we should point out that events surrounding Jesus’ arrival in Gennesaret (Mark 6:53–56) is strikingly similar to the events described in Mark 1:32–34. In Mark 1, Jesus concludes the evening with prayer; in Mark 6, he prepares for the wave of people that will hit him on the beaches of Gennesaret. It could be, however, that Peter just recalls these opportunities to pray, in which case the first reason would be the dominant explanation for why Jesus prayed. Peter, for some reason, does not mention how Jesus withdrew to the mountain to pray all night before naming twelve individuals as his apostles. Luke does (6:12–16). That Peter did not highlight Jesus’ night in prayer to God before naming the apostles at least casts some doubt on whether the reason for prayer in Mark 1 is connected to a critical juncture in Jesus’ ministry. It is better to view Jesus’ attention to prayer in Mark as opportunities to gather some strength and focus his mind on the things above before he moves on to what lies ahead in his ministry.