In order to reinforce the principle of a holy nation, G-d tied Pesach, the time of national liberation, to Shavuot, the time of the Giving of the Torah, via the Sefirat HaOmer, the “counting of the Omer”. The counting is also tied to the Land, for it begins with the harvesting of the Omer. This is why our sages declared (Menachot 83b), “All communal and individual offerings can come from the Land of Israel or from outside of it, from new grain or from old, except for the Omer and the two loaves of Shavuot, which can only be brought from new grain and from the Land.” The mitzvah of the Omer bound Pesach to Shavuot and the people to their holiness. It completed the creation of Israel as a holy nation and ensured that this holy nation would merit Eretz Yisrael. Our sages said (Vayikra Rabbah, 28:6): Never take the mitzvah of the Omer lightly, for Abraham merited through it to inherit the Land. It says, “To you and your offspring will I give the land where you are now living as a foreigner. The whole land of Canaan” (Gen. 17:8), and this was so that Abraham “would keep G-d's covenant” (Ibid., v. 9). By fulfilling the mitzvah of the Omer, which ties Pesach to Shavuot, and thereby becoming a holy nation, Israel merited to inherit the Land from the nations; for had they not agreed to be a holy nation, why should G-d have taken the Land from the nations and given it to them?
Our sages ask why the Torah was not given immediately or shortly after Israel left Egypt, and they answer (Kohelet Rabbah, 3:2): When Israel left Egypt, they were worthy of receiving the Torah immediately. Yet ... G-d said, “My children have not yet attained their lustre. They emerged from an enslavement of mud and bricks, and shall I give them the Torah? Let them enjoy two or three months of the Manna, well-water [Miriam's well that miraculously followed Israel] and quails, and then I shall give it to them.” Nonetheless, the nation's faith was weak and abated very quickly. As our sages (Shemot Rabbah, 5:14): “Moses and Aaron then went to Pharaoh” (Ex. 5:1): And where did the elders go that they were not mentioned together with Moses and Aaron, when G-d had previously said to Moses, “you and the elders will go” (Ex. 3:18)? Our sages answered, “The elders went with them, yet they stole away... and disappeared. By the time Moses and Aaron reached the palace, not one remained.” Numerous other sources testify to Israel's lack of faith then. G-d, therefore, demanded of them at least a small sign of faith, albeit fleeting, before He would redeem them, because faith and trust are the root of serving G-d. Without them, without faith in the King, Redeemer and Savior, there is no Torah. Therefore, the counting of the Omer not only underscores the bond between the people and holiness, between a holy nation and its holy land, but also establishes the formation of the people on the basis of faith. The Omer was harvested from the new grain, and until then it was forbidden to eat new grain and forbidden even to harvest it. As Rambam wrote (Hilchot Temidim U'Musafin 7:13), “It is forbidden to harvest in Eretz Yisrael any one of the five species of grain before the Omer is harvested.” Through this, we proclaim that G-d gives bread to all flesh and that we depend on Him for this grain, for His blessings, for His dew and His rain. Therefore, the first cutting is given to G-d as the meal offering, as an announcement that we have placed our hope in Him with faith and trust, and as an acknowledgment and giving of thanks for blessing us with this harvest.
This idea is also alluded to in the law that this Omer comes from barley (Menachot 68b), an animal food, as with the meal offering of the Sotah, the suspected adulteress, and of the Sotah we find: All of the meal offerings come from wheat [a food consumed by humans] but [the meal offering of the Sotah] comes from barley [consumed by animals]... R. Gamliel says, “Just as her deeds were bestial, so is her offering from the food of the beast.” (Sotah 14a). All this is so even though the Omer meal offering is not entirely like the Sotah offering, since the former requires oil and frankincense, whereas the latter does not. Furthermore, the former is brought as geresh, the finest grade barley flour (not normally consumed by animals), whereas the Sotah barley offering is brought as regular barley flour, the way animals eat it. Even so, G-d wished to hint to us at the start of the new grain that man, like the animal, depends on G-d's mercy. As King David described in Psalms (104:27), “All of them wait for You, that You may give them their food in due season.” Our sages furthermore said (Vayikra Rabbah, 28:3): It says, “Neither say they in their heart:'Let us now fear the L-rd our G-d, Who gives the early and late rain in due season'” (Jer. 5:24). [Let him not say], “Once G-d gives you everything, you no longer need Him.” “Who keeps for us the appointed weeks of the harvest” (Ibid.). G-d will protect us from evil winds and evil dews. When? During the seven weeks between Pesach and Shavuot. In other words, we should not think that since the winter has passed and there was rain, and there is already grain, there is no more need to pray to G-d regarding this grain. Even when there is grain, if during harvest time rain falls and there are evil winds and evil dews, the grain will be ruined. As Samuel said, “Is it not wheat harvest today? I will call unto the L-rd that He may send thunder and rain... and all the people greatly feared the L-rd and Samuel” (I Samuel 12:17-18). For this reason, the Omer meal offering is waved, as our sages said (Vayikra Rabbah 28:5): How would he wave it? R. Chama bar Ukva said in the name of R. Yossi bar Chanina, “He passes it back and forth, and up and down. He passes it back and forth for the One Who owns the entire universe, and he raises it up and down for Him Who owns those in Heaven and earth.” R. Simon, son of R. Yehoshua says, “He passes it back and forth to cancel harsh winds, and he raises and lowers it to cancel harsh dews.” The main point here is that faith is a fixed component of the Omer meal offering, because the meal offering itself symbolizes faith. Indeed, G-d established this interlude between national liberation and sanctification in order to exalt and refine Israel with mitzvot and values, precisely those of faith and trust in G-d – the manna, the well and the quail. All three served as signs that the sustenance and survival of man on the individual and national level are solely in G-d's hands.
As our sages said (Pesikta Rabbati, 18): G-d said to Israel, “My children, when I used to give you the Omer [of manna that fell for each person], I would give each of you 'an Omer per person, according to the number of people each man has in his tent' (Ex. 16:16). Now that you are giving Me the Omer, you give Me only one Omer from all of you collectively.” We see that the waving of the Omer, which makes the new grain permissible, serves as a reminder of the Omer of the manna, and as a symbol of Israel's faith and trust in G-d. From here, we learn that even physical and national liberation do not make the people fit to assume the mantel of holiness. After all, a secular nation, like all the nations, surely thinks exclusively in nationalist, “realistic” terms. For such a nation, only the size of its army and the quantity of arms and allies can make them secure. They must advance to this by keeping mitzvot which express concepts, values and trust in G-d, which refine and elevate the nation from base secular nationalism.