The most immediately notable thing about this number is that it is the digit reversal of 37. Thirty seven represents the "Word of God". Both numbers use digits 3 and 7, which are two of the four "perfect numbers" and represent divine perfection and spiritual perfection respectively. It might be expected that the symbolic meaning of seventy three will be related to all of these facts.
Seventy three is not itself mentioned in the Bible. However we have some indirect clues as to what this number might represent. Possible the best "clue" is the relationship between the numbers 73 and 37. This relationship is perhaps best seen geometrically. However the bible also ties the two numbers together. The numeric value of the first verse of the Bible is 2701 = 37 x 73. Further the number of verses in the book of Genesis, the first book of the Bible, is 1533 = 3 x 7 x 73. But before looking at these phenomenon in detail let us consider the geometric relationship between the two numbers.
Seventy Three and Thirty seven are also related geometrically. Thirty seven can be arranged as a perfect hexagon. If we then add a triangle to each side of the hexagon, we get a hexagram of 73. While the digit reversal relation ship between the two numbers is dependent on the number system we write the numbers in, the geometric relationship is not. It we write 37 and 73 in binary, or Roman numerals, or Egyptian symbols, the digit reversal "trick" no longer works but the geometric relationship is still present.
Starting with one counter we can add a layer of six more counters around it. This produces a simple hexagon (six sides) with seven counters in it. While one is really the first number of the series of "hexagonal numbers" seven is really the first actual hexagonal number. Adding another layer produces a hexagon of 19, and a third layer a hexagon of 37. Also it is interesting that 37 is related to its own digits geometrically. The first hexagonal number is seven (7), and 37 is the third (3) hexagonal number. Also note the the diameter of the 37 hexagon, from one corner to its opposite, is seven (7).
We can also add a triangle of counters to each face of the hexagons that we generate. Thus to the first hexagon of seven we add six counters, one for each face. This produces a "star of David" shape (also called a hexagram) with thirteen counters in it. Thus thirteen is the first "hexagram number". If we add a triangle of counters to the second hexagonal number we get a hexagram of 37 counters. Thus 37 is both the second hexagram and the third hexagon. If we add a triangle of counters to the third hexagonal number we get a hexagram of 73 counters. Thus we can see that 73 is the hexagram of the 37 hexagon. Their geometric relationship is simple and profound.
There is more, as already noted 37 is a hexagram as well as a hexagon. So 37 is the second hexagram number and 73 is the third hexagram number. Thus 37 as a hexagram neatly sits inside 73 as a hexagram. The number of counters around the central 37 is 36. ie. the outer layer of the 73 hexagram is 36 or 73-37=36. Since 36 = 6 x 6, we have the Word of God (37) centermost, surrounded by the natural man, adding to 73. So perhaps 73 is best thought of as representing those who can bear witness of the things of God.
Another interesting point about these numbers is that in the 73 hexagram if the counters are numbered, the central counter is the 37th. Thus 37 is central to 73 as well as being its inverse.
The 73rd Verse
And unto Adam he said, Because thou hast hearkened unto the voice of thy wife, and hast eaten of the tree, of which I commanded thee, saying, Thou shalt not eat of it: cursed is the ground for thy sake; in sorrow shalt thou eat of it all the days of thy life;
The seventy third verse of the bible is the beginning of the judgement upon Adam for his disobedience. He listened to the voice of his wife rather than remembering the commandment of God. Thus this verse is a judgment for not listening and obeying God rather than some other. Further than that there is the curse upon the ground and the statement that "in sorrow thou shalt eat of it all the days of thy life". Thus every time they were to eat, they would be reminded of their disobedience, and thus reminded of what they should have done. Thus the ground was not just to be cursed unto them, but a witness unto them and indirectly a witness unto God, whom they should have obeyed. Thus in this verse one of the themes whould be "bearing witness to God", witness of His righteous judgments and gracious mercy.
The 73rd Chapter
The seventy third chapter of the Bible is Exodus chapter 23. The chapter is basically a collection of commandments.