NKJV - 7 Jesus said to them, "Fill the waterpots with water." And they filled them up to the brim.
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I would like to indicate that this question actually has a much broader application.
It startes with Joseph's interactions with his brothers, when he placed a cup in the bag of corn. Note that the cup is empty and the corn was not bread yet.
When Joseph reveals himself to his brothers, he told them that all the things that happened was on purpose "so that they would be safed"
The first miracle that Jesus performed has critical importance, he knew what will happen at the Last Supper. He had to demonstrate that he can change water into wine and that it will confirm the wonder and powerful miracle when he tells His disciples " take this cup, it is my blood" Because He has demonstrated that by spoken word He has the power to change the water into wine, He can now declare " take this cup it is my blood "
From creation to His crucifixion the act of forgiveness was the altar. From His crucifixion to His return the act of his forgiveness is at His table.
The corn that was in Joseph's bag, is now the bread that signifies His body has gone through the fire, so that we don't have to.
The pots was filled to the brim, that signifies that His grace is abundantly, but more than that, the pots will never get empty.