From “The Life and Times of Jesus the Masiah”, Alfred Edersheim
Book II chapter 6 line 20-23states:
A passage in the Mishnah20 leads to the conclusion, that the flocks, which pastured there, were destined for Temple-sacrifices,21 and, accordingly, that the shepherds, who watched over them, were not ordinary shepherds. (**21. In fact the Mishnah (Baba K. vii. 7) expressly forbids the keeping of flocks throughout the land of Israel, except in the wilderness – and the only flocks otherwise kept, would be those for the Temple-services (Baba K. 80 a)
The latter were under the ban of Rabbinism,22 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 Mishnic 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.23 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.
Grace and Peace 