Benson Commentary:

It seems there was a considerable number of the shepherds together here, for the expression implies that they watched by turns according to these divisions of the night. “As it is not probable,” says Dr. Doddridge, “that they exposed their flocks to the coldness of winter nights in that climate, where, as Dr. Shaw (Trav., p. 379) has shown, they were so very unwholesome, it may be strongly argued from this circumstance that those who have fixed upon December for the birth of Christ have been mistaken in the time of it.” The birth of Christ has been placed in every month of the year. The Egyptians placed it in January — Wagenseil, in February — Bochart, in March — some mentioned by Clement of Alexandria, in April — others, in May — Epiphanius speaks of some who placed it in June — and others who supposed it to have been in July — Wagenseil, who was not sure of February, fixed it probably in August — Lightfoot, on the 15th of September — Scaliger, Casaubon, and Calvisius, in October — others, in November. But the Latin Church, being infallible in judgment, and supreme in power, has settled the matter by declaring that he was born on the 25th of December.

Ellicot’s Commentary:

Shepherds abiding in the field.—The fact has been thought, on the supposition that sheep were commonly folded during the winter months, to have a bearing adverse to the common traditional view which fixes December 25 as the day of the Nativity. At that season, it has been urged, the weather was commonly too inclement for shepherds and sheep to pass the night in the open air, and there was too little grass for pasturage.

In summer, on the other hand, the grass on the hills is rapidly burnt up. The season at which the grass is greenest is that just before the Passover (Mark 6:39; John 6:10); and, on the whole, this appears the most probable date. The traditional season, which does not appear as such till the 4^th century, may have been chosen for quite other reasons—possibly to displace the old Saturnalia, which coincided with the winter solstice. It is noticeable that the earliest Latin hymns connected with the festival of Christmas dwell on the birth as the rising of the Sun of Righteousness on the world’s wintry darkness.

Matthew Poole’s Commentary:

Bethlehem was a place about which were pastures for sheep, as appears from 1 Samuel 17:15. There were shepherds abroad in the night (for so the word signifieth) watching over their flocks; whether the phrase signifieth (as some think) successive watches, such as are kept by soldiers, and by the priests, I cannot say. This maketh some think, that it is hardly probable that our Saviour was born in December in the midst of the winter, that being no time when shepherds use in the night to be keeping their flocks in the field.

Gill’s Exposition:

abiding in the field, watching over their flock by night: from whence it appears, that Christ was born in the night; and the (o) Jews say, that the future redemption shall be in the night; and Jerom says (p), it is a tradition of the Jews, that Christ will come in the middle of the night, as was the passover in Egypt: it is not likely that he was born, as is commonly received, at the latter end of December, in the depth of winter; since at this time, shepherds were out in the fields, where they lodged all night, watching their flocks: they were diligent men, that looked well to their flocks, and watched them by night, as well as by day, to preserve them from beasts of prey; they were, as it is in the Greek text, “keeping the watches of the night over their flock.” The night was divided into four watches, the even, midnight, cock crowing, and morning; and these kept them, as the Arabic version adds, alternately, some kept the flock one watch, and some another, while the rest slept in the tent, or tower, that was built in the fields for that purpose.