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And it is written: “That he shall write for himself a second (mishneh) Torah” (Deuteronomy 17:18) — a script that is apt to be changed (lehishtannot)
Some of the most ancient surviving Hebrew texts are written in what looks, to the untrained eye, like chicken scratch. This is the original Hebrew script that scholars call Paleo-Hebrew. The Hebrew script that we are familiar with doesn’t appear in the Jewish historical record until after the Jews returned from the Babylonian exile in 538 BCE, during the time of Ezra the scribe. This newer script was adapted from the Aramaic alphabet, the standard alphabet of the Babylonian Empire. While most of the biblical manuscripts found among the Dead Sea Scrolls (dating from the third century BCE to the first century CE) are written in this new alphabet, many continue to spell out the Tetragrammaton, the four-letter name of God, in Paleo-Hebrew. Presumably, the authors of these scrolls associated this older script with God and increased holiness.
Eventually, the practice of writing even God’s name in Paleo-Hebrew fell out of favor, and all Hebrew texts were written in the newer script — the one familiar to us — based on Aramaic. Though this may be the first time you’re hearing about Paleo-Hebrew, the rabbis of the Talmud were well aware of it.