Shema Yisrael Hashem Elokeinu Hashem Echad (Devarim 6:4)
The last letter (Ayin) of the word for Shema is written larger than the rest and so is the last letter, Daled, of the word Echad. What's the significance of these deviations?
Maybe the letters are large to teach us that the smallest of deviations could pervert the meaning of a text.
For example, if one would read the Shema as having an Aleph as its last letter (after all the Aleph and Ayin are both silent letters), the word Shema would mean "perhaps" (sheh-mah). This would change a firm declaration of belief into an expression of doubt.
And if the Daled would be mistaken for a Reish (after all, there is only a slight difference in the writing of a Daled and Reish), the word Echad (One) would be read Acher (other). This would change belief in One G-d into a belief in two gods.
As we move towards Rosh Hashanah and Yom Kippur, all of us ought to be careful with every word, every gesture and every action. Because in life, the smallest differences make all the difference in the world.
