There are, roughly, 666 million evangelicals who spend their Advent season (OK, most don't have a clue about Advent) trying to disprove the accurate historical date of The Incarnation by citing the Shepherds in the field and claiming that "it was too cold" and so that proves Jesus wasn't born on the 25th and that date really is the date of Sol Invictus which means the Catholic Church is suffused with paganism blah, blah, blah...
Well, here is an unimpeachable source in that the source is Jewish and he wrote a book that proves that there WERE shepherds in the field with their flocks at that time - and that they were there tending their sheep who were intended for sacrifice - talk about an unintended proof of birth of The Saviour, The Lamb of God, who was to die for our sins as an act of propitiation....
In any event, here is Edelsheim: Alfred Edersheim, in his "The Life and Times of Jesus"
And yet Jewish tradition may here prove both illustrative and helpful. That the Messiah was to be born in Bethlehem, was a settled conviction. Equally so, was the belief , that He was to be revealed from Migdal Eder, 'the tower of the flock.' This Migdal Eder was not the watchtower for the ordinary flocks which pastured on the barren sheepground beyond Bethlehem, but lay close to the town, on the road to Jerusalem. A passage in the Mishnah [951] leads to the conclusion, that the flocks, which pastured there, were destined for Temple-sacrifices [952], and, accordingly, that the shepherds, who watched over them, were not ordinary shepherds. The latter were under the ban of Rabbinism, on account of their necessary isolation from religious ordinances, and their manner of life, which rendered strict legal observance unlikely, if not absolutely impossible. The same Mishnaic passage also leads us to infer, that these flocks lay out all the year round, since they are spoken of as in the fields thirty days before the Passover -- that is, in the month of February, when in Palestine the average rainfall is nearly greatest.
Thus, Jewish tradition in some dim manner apprehended the first revelation of the Messiah from that Migdal Eder, where shepherds watched the Temple-flocks all the year round. Of the deep symbolic significance of such a coincidence, it is needless to speak.
It was, then, on that ‘wintry night’ of the 25th of December, that shepherds watched the flocks destined for sacrificial services, in the very place consecrated by tradition as that where the Messiah was to be first revealed.
Thus, Jewish tradition in some dim manner apprehended the first revelation of the Messiah from that Migdal Eder, where shepherds watched the Temple-flocks all the year round. Of the deep symbolic significance of such a coincidence, it is needless to speak.
It was, then, on that ‘wintry night’ of the 25th of December, that shepherds watched the flocks destined for sacrificial services, in the very place consecrated by tradition as that where the Messiah was to be first revealed.