" By virtue of the Omer that I counted today…may I be purified and sanctified with the sanctity from above, and may this cause an influence of great abundance in all the worlds."(Seder Sfirat HaOmer, terminating prayer).
At the conclusion of each night's counting of the Omer, we ask Hashem that we be purified and sanctified. We also say that our purification and sanctification triggers an influence of tremendous abundance in all the worlds – both material and spiritual.
Before attempting to comprehend the above principles, we have to realize that the people of Israel at Pesach are a nation of newly redeemed slaves. Not only were we newly redeemed slaves at the time of our exodus from Egypt, but every year at Pesach as well. Pesach is the furthest time of the year from the High Holidays of Rosh Hashanah and Yom Kippur, when all of Israel makes tshuva out of the awe of Hashem. As the long winter months transpire, we drop our guard and fall slaves to our bodily urges and appetites.
At Pesach time, we complete a process of physically cleaning our domains from chometz, or leavened agents, and begin a spiritual process of cleaning our hearts as a preparation for freedom. Tshuva is the cleansing of the heart from all evil.
True freedom, which includes the liberty from social pressure and bodily urges, comes only from Torah. Therefore, even though we break off the chains of bondage at Pesach, we're not really free until we receive the Torah 50 days later on Shavuot. During the interim 49 days, we count the Omer as a process of preparing ourselves to receive the Torah. Rebbe Nathan of Breslev says that each of the 49 days corrects a character attribute that corresponds to the 48 ways of attaining Torah (see tractate Avos, 6:6 for the entire list), while the 49th day serves as a correction to our prayers.
Rebbe Nathan writes (Abridged Likutei Moharan 63:2) that the 49 days of the Omer also correspond to the 49 gates of Tshuva. By reciting Tehillim (Psalms) every day, one can open each gate of Tshuva. Therefore, concludes Rebbe Nathan, saying Tehillim during each day of the Omer is extremely important.
Rebbe Nathan's principle of Tehillim and Tshuva explains how the purification of our souls during the days of the Omer invokes abundance in all the worlds, as we shall see – with Hashem's grace – in the following parable: