(Excerpt from Chumash Mesoras Harav)
כַּקָּטֹן כַּגָּדֹל תִּשְׁמָעוּן – you shall hear the small just as the great.
Based on this verse, Resh Lakish rules (Sanhedrin 8a), This indicates that you must be as concerned with a lawsuit concerning one perutah as with a suit concerning a hundred maneh. The Talmud’s question there is interesting: For what practical purpose is this laid down? If it is to urge the need to give equal consideration and investigation, is this not self-evident? That is, the judge must devote as much thought to a case concerning a penny as to that concerning ten thousand dinars, and must adjudicate as truthfully. But this, says the Talmud, is self-evident and would not call for a specific Biblical verse. The Talmud then answers: [The meaning is] that the case must be given due priority, if it should be first in order. The quotation was needed to demonstrate that judges must not give precedence to cases involving a sum of ten thousand dinars over cases involving a mere penny. If a case involving a penny comes up first, it must be dealt with prior to one concerning a sum of a million; judgement must not be deferred until afterwards.
One can discern far-reaching implications in this halachic principle. Regarding real estate, ownership changes with the transfer of money. How much money must the buyer give the seller to gain the right to a piece of land? The whole price? Most of it? Half of it? The law is that a single coin changing hands is sufficient to establish the purchase. If a man buys a skyscraper worth fifty million dollars and hands over a single penny to the seller, then he has gained rights of possession to it.
In Psalms 147:6, we come across the phrase לִתְבוּנָתוֹ אֵין מִסְפָּר – His understanding is beyond calculation. This phrase can also be translated as His wisdom has no number. Although the Creator fashioned millions of stars, giant solar systems which stretch across huge distances measured in millions of light-years, His wisdom has no number; large numbers are of no significance to Him. In Judaism, the tiny quantity can be immeasurably significant. Even a trace of chametz that falls into a large quantity of food renders the whole mixture prohibited on Pesach. The Torah requires one to set aside terumah, a portion of his crop for the kohanim, yet the offering of even a single grain is considered sufficient to fulfill one’s formal Biblical obligation. (Teshuvah Lecture, 1972)