Daf Yomi Inisghts - Berachos 32

At the time of the עגל הזהב, Golden Calf, Hashem told Moshe לך רד, go down. The Sefer Tiyul BePardes points out the significance of the word רד. In the Pasuk of לא תשתחוה לאל אחר, do not bow down to other gods, the letter ר of אחר, other, is written large. Similarly, in the Pasuk of שמע ישראל ה' אלוקינו ה' אחד, Hear O Israel God is our Almight, God is One, the letter ד of אחד, one, is written large. These two letters, ר and ד, are very similar and there is only a small point that differentiates between them. They are written large in the Torah to remind you not to confuse the ר of other gods with the ד of the One God. God was now telling Moshe that לך רד, go, your people have confused ר and ד and substituted other gods for the one God.
I have seen this concept expressed by the curse given to Adam as well. Among the things God said to Adam was קוץ ודרדר תצמיח לך, literally thorns and thistles will grow for you. Kabbalistic works point out that it is a thorn which separates between the letter ד and the letter ר, just a small point of ink. God was warning Adam about the challenge of that thorn and the result of that challenge will be דרדר, an existence in which man will keep changing from ד to ר and back again. We will live in an existence in which there are times that we will be able to discern the Unity of God symbolized by the ד and then other times when we are challenged to see God's Unity clearly and we stray towards the ר of other gods. And that process will constantly repeat itself.