Iyar and Rosh Chodesh Iyar, in Context of Year
1 Nisan (30 days)
2 Iyar (29 days - Rosh Chodesh always 2 days)
3 Sivan (30 days)
Biblical Significance of Rosh Chodesh Iyar
The first Rosh Chodesh after the Exodus fell on Shabbat, and the Jewish People found themselves, after the great miracle of "Kriat Yam Suf," the Splitting of the Sea of Reeds, at Marah. That place was given its name, which means "bitter," by the fact that the water there was, in fact, quite bitter, and not drinkable.
The people, having exhausted their supply of water, turned to Moshe, and asked, "What shall we drink?" Seeing the legitimacy of their complaint, Moshe brought it, so to speak, to G-d's attention. Whereupon, Hashem indicated to Moshe a certain tree, and told him to throw it into the water. This was very peculiar, because the tree itself was also bitter. However, once it entered the water, the waters turned sweeter than the best bottled water!
How is that possible, you ask? Bitter with bitter, yielding sweet? Two answers, of course, are possible. The first is that Hashem may have been working outside the realm of the Laws of Nature, and it was an "open miracle." Alternatively, having created them, the Creator was intimately familiar with the chemical make-up of both the tree and the water, and "knew," so to speak, that when this bitter ingredient reacted with the other bitter ingredient, the result would be sweet!
On the first of Iyar, in the second year after the Exodus, the first census of the Jewish People began, at the command of G-d. A unique feature of this census was that each member of the People of Israel knew and could trace his or her lineage back to the sons of Yaakov, some two hundred years earlier.
As a result of the census, each individual found his or her exact place in the tribe, and each tribe took its place in the four-fold formation of tribes. Each formation consisted of three tribes, and each had its own flag, reflecting the characteristics of its component tribes. The formations arrayed themselves around the Mishkan when they camped, and when the People moved through the desert, they marched in these formations as well, led by the pillar of cloud. A fantastic and formidable sight!