The Meaning of Numbers: The Number 73
The possible meaning of the number 73 is derived primarily from its use in the Book of Psalms.
The songs that compose the Book of Psalms, in their original inspired order, were divided into five sections. Song 73 is in a set that contains the fewest writings at seventeen.
"In the original Hebrew apportionment of the Book of Psalms, the 150 psalms are assorted among five major divisions. These five "books" are not discernible in the ordinary King James Version, but they are evident in the Hebrew manuscripts" (Restoring the Original Bible by E. Martin, Appendix One).
Psalm 1 to 41 was the first section of this book in the originally inspired Old Testament, 42 to 72 the second, 73 to 89 the third, 90 to 106 the fourth and 107 to 150 the last.
It is no accident that Psalm 73 begins the third major division of the Psalms. It, as well as others in this third set, all share a general common theme centering on Jerusalem's temple. Additionally, several of them also comment on themes surrounding its destruction.
If I say, "I will speak thus;" behold, I would have betrayed the generation of Your children. When I thought to understand this, it was too painful for me until I went into the sanctuary of God; then I understood their end (Psalm 73, verses 15 - 17).
A bloody moon and number seventy-three
The book of Joel numbers 3 chapters and 73 total verses. Joel, one of the Minor Prophets, is the only Old Testament prophetic book to mention the moon turning to blood before the return of Jesus Christ.
And also I will pour out My Spirit upon the servants and upon the handmaids in those days. And I will show wonders in the heavens and in the earth - blood and fire and pillars of smoke.
The sun shall be turned into darkness, and the moon into blood, before the coming of the great and awesome day of the Lord (Joel 2:29 - 31, see also Revelation 6:12).
Asaph and the number 73
Psalm 73 is one of twelve psalms believed to be written by or for Asaph. The other songs by him are Psalms 50 and 74 through 83.
Asaph's songs were so cherished, partly because he possessed the gift of prophecy (1Chronicles 25:1 - 2), that King Hezekiah sung them after cleansing and rededicated Jerusalem's temple for the worship of God.
Then Hezekiah the king and the rulers commanded the Levites to sing praise to the Lord with the words of David and of Asaph the seer. And they sang praises with gladness, and they bowed their heads and worshiped (2Chronicles 29:30, HBFV).
More info on Biblical Meaning of 73
Nehemiah 7 is the only Biblical chapter that has exactly 73 verses. This chapter is also the fourth largest in the Old Testament in terms of number of verses. Only 1Chronicles 6, Numbers 7 and Psalm 119 has more verses in the King James Bible.