שָׁמוֹר אֶת חֹדֶשׁ הָאָבִיב וְעָשִׂיתָ פֶּסַח לַה’ אֱלֹקֶיךָ כִּי בְּחֹדֶשׁ הָאָבִיב הוֹצִיאֲךָ ה’ אֱלֹקֶיךָ מִמִּצְרַיִם לָיְלָה – דברים טז, א
The Torah commands us to structure the calendar in a manner that ensures a spring arrival for the 14th of Nissan, the day Pesach begins. The emphasis placed on the timing of this holiday for the springtime highlights the uplifting message conveyed by the season of spring.
During the months of winter, there are almost no visible signs of plant life. When the winter season concludes, however, the processes of growth that lie dormant in the earth suddenly spring to life. It then becomes evident that the lack of growth that we witnessed in the winter had been only a temporary pause, to allow for nature’s rejuvenation. Now, a fresh season can blossom and thrive.
This idea is also hinted in the holiday of Pesach. Bnei Yisrael suffered bitterly in Egypt, exiled and oppressed in both body and spirit. Only later was it revealed that the exile in Egypt had in fact refined Bnei Yisrael (see Devarim 4:20, Rashi), enabling them to receive the Torah — the very word of G-d — a short fifty days after leaving Egypt.
The same is true for the individual. If we ever experience a period in life that seems to be barren, with no signs of productivity or growth, we must realize that this barrenness is almost certainly not the permanent reality. It is merely a temporary break in order to to strengthen us, to allow for us to ultimately blossom and flourish.
—Igros Kodesh, vol. 4, pp. 267-268