Objection 1. It would seem that Christ should not have associated with men, but should have led a solitary life. For it behooved Christ to show by His manner of life not only that He was man, but also that He was God. But it is not becoming that God should associate with men, for it is written (Daniel 2:11): "Except the gods, whose conversation is not with men"; and the Philosopher says (Polit. i) that he who lives alone is "either a beast"--that is, if he do this from being wild--"or a god," if his motive be the contemplation of truth. Therefore it seems that it was not becoming for Christ to associate with men.
Objection 2. Further, while He lived in mortal flesh, it behooved Christ to lead a most perfect life. But the most perfect is the contemplative life, as we have stated in the II-II, 182, 1,2. Now, solitude is most suitable to the contemplative life; according to Hosea 2:14: "I will lead her into the wilderness, and I will speak to her heart." Therefore it seems that Christ should have led a solitary life.
Objection 3. Further, Christ's manner of life should have been uniform: because it should always have given evidence of that which is best. But at times Christ avoided the crowd and sought lonely places: hence Remigius [Cf. Catena Aurea, Matth. 5:1], commenting on Matthew, says: "We read that our Lord had three places of refuge: the ship, the mountain, the desert; to one or other of which He betook Himself whenever he was harassed by the crowd." Therefore He ought always to have led a solitary life.
On the contrary, It is written (Baruch 3:38): "Afterwards He was seen upon earth and conversed with men."
I answer that, Christ's manner of life had to be in keeping with the end of His Incarnation, by reason of which He came into the world. Now He came into the world, first, that He might publish the truth. thus He says Himself (John 18:37): "For this was I born, and for this came I into the world, that I should give testimony to the truth." Hence it was fitting not that He should hide Himself by leading a solitary life, but that He should appear openly and preach in public. Wherefore (Luke 4:42-43) He says to those who wished to stay Him: "To other cities also I must preach the kingdom of God: for therefore am I sent."
Secondly, He came in order to free men from sin; according to 1 Timothy 1:15: "Christ Jesus came into this world to save sinners." And hence, as Chrysostom says, "although Christ might, while staying in the same place, have drawn all men to Himself, to hear His preaching, yet He did not do so; thus giving us the example to go about and seek those who perish, like the shepherd in his search of the lost sheep, and the physician in his attendance on the sick."
Thirdly, He came that by Him "we might have access to God," as it is written (Romans 5:2). And thus it was fitting that He should give men confidence in approaching Him by associating familiarly with them. Wherefore it is written (Matthew 9:10): "It came to pass as He was sitting... in the house, behold, many publicans and sinners came, and sat down with Jesus and His disciples." On which Jerome comments as follows: "They had seen the publican who had been converted from a sinful to a better life: and consequently they did not despair of their own salvation."
Reply to Objection 1. Christ wished to make His Godhead known through His human nature. And therefore, since it is proper to man to do so, He associated with men, at the same time manifesting His Godhead to all, by preaching and working miracles, and by leading among men a blameless and righteous life.
Reply to Objection 2. As stated in the II-II, 182, 1; SS, 188, 6, the contemplative life is, absolutely speaking, more perfect than the active life, because the latter is taken up with bodily actions: yet that form of active life in which a man, by preaching and teaching, delivers to others the fruits of his contemplation, is more perfect than the life that stops at contemplation, because such a life is built on an abundance of contemplation, and consequently such was the life chosen by Christ.
Reply to Objection 3. Christ's action is our instruction. And therefore, in order to teach preachers that they ought not to be for ever before the public, our Lord withdrew Himself sometimes from the crowd. We are told of three reasons for His doing this. First, for the rest of the body: hence (Mark 6:31) it is stated that our Lord said to His disciples: "Come apart into a desert place, and rest a little. For there were many coming and going: and they had not so much as time to eat." But sometimes it was for the sake of prayer; thus it is written (Luke 6:12): "It came to pass in those days, that He went out into a mountain to pray; and He passed the whole night in the prayer of God." On this Ambrose remarks that "by His example He instructs us in the precepts of virtue." And sometimes He did so in order to teach us to avoid the favor of men. Wherefore Chrysostom, commenting on Matthew 5:1, Jesus, "seeing the multitude, went up into a mountain," says: "By sitting not in the city and in the market-place, but on a mountain and in a place of solitude, He taught us to do nothing for show, and to withdraw from the crowd, especially when we have to discourse of needful things."
Source: Summa Theologica (New Advent)