Why is the letter ב closed on all sides and open in the front? This teaches us that it is the House (בַּיִת) of the world. God is the place of the world, and the world is not His place. Do not read ב, but בַּיִת (house). It is thus written (Proverbs 24:3), "With wisdom the house is built, with understanding it is established."
What does the ב resemble? It is like a man, formed by God with wisdom. He is closed on all sides, but open in front. The א, however, is open from behind. This teaches us that the tail of the ב is open from behind. If not for this, man could not exist. Likewise, if not for the ב on the tail of the א, the world could not exist.