Theophylact of Ohrid

Note, if you will, the Lord's modesty here as well. He remains alone by the road while the disciples have gone off to the city to buy food. They considered the needs of the stomach so secondary that at a time when nearly everyone had already dined and was resting, they were only just buying food — that is, bread alone — so that we too might learn not to concern ourselves with a variety of dishes.

Commentary on John ↗

Thomas Aquinas

Christ had the opportunity to ask this of the woman because his disciples, whom he would have asked for the water, were not there, thus the Evangelist says, His disciples had gone to the town. Here we might notice three things about Christ. First, his humility, because he was left alone. This is an example to his disciples that they should suppress all pride. Someone might ask what need there was to train the disciples in humility, seeing that they had been but lowly fishermen and tentmakers. …

Commentary on John ↗

Bonaventure

"But His disciples had gone into the city to buy food." He rightly says "to buy," not to seek gratuitously, because there was no one there who would give: whence it is said in Luke 9: "The disciples entered into a city of the Samaritans, to prepare for Him: and they did not receive Him, because His face was of one going to Jerusalem." It is asked concerning what it says, that the disciples had gone into the city to buy food. The disciples were Jews: therefore they ought not to have dealings with Samaritans. …

Commentary on John, Chapter 4 ↗