Why did they not cross over by the dry land where the Suez Canal now exists?

The Catholic Answers

It is not certain that the contour of the country was the same then as now. Some authorities say that the Red Sea swept much farther inland in earlier times, including even the bitter lakes. In any case, under God’s direction, the Jews were led away from the dry sections we now know, as described in Numbers ch. 33, that He might show His power and protection, and that the Egyptians might be justly punished, as shown by Exod. XIV., 2.

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