Money plays a significant role in Lessing's Nathan the Wise. Although there are far more than three scenes that show the significant role of money, I can name three right off the bat. Keep in mind the stirring description of Nathan the Wise:
[Nathan the Wise was given] the greatest gift, wisdom, and the most worthless, riches.
Nathan Helps a Stranger
Nathan unknowingly meets Conrad von Stauffen along the road and thinks him a stranger without a cent to his name. Nathan gives a true offer of friendship which the Templar first refuses, but then accepts in the form of buying him a mantle because Conrad no longer has one because it has been burned. Note the original tone used here:
If you insist upon a reward, this mantle was slightly scorched in the flames when I rescued your daughter ... When it is all in rags ... I will come to borrow the money from you to buy another.
Nathan the Wise sheds tears here, and this erases the Templar Conrad's hatred. The scene ends with Nathan and the Templar shaking hands. It is only at this point that Nathan the Wise learns that the young Templar is truly Conrad von Stauffen. In this instance, money is important because it is a gesture of true friendship: giving to another who is thought to be truly "the least of my brethren." Nathan then states a wonderful truth:
There are good men in every land. The tree of life has many branches and roots. Let not the topmost twig presume to think that it alone has sprung from mother earth.... We did not choose our races for ourselves. Jews, Moslems, Christians--all alike are men. Let me hope I have found in you--a man.
Saladin Summons Nathan the Wise
After the young knight and Recha fall in love at first sight, he does leave quickly due to his loyalty to Nathan. Why? Saladin has asked for audience with the Jew because Saladin wants to replace the treasury. This crusade going on that pits Christian against Muslim might continue, and for the Saladin to have a chance, the treasury must be replenished with money. Here money represents the winning side of any fight. Saladin assumes that to win this Crusade against the Christians, the money must be put back into the treasury. Without this money, the Christians are sure to win.
The Parable of the Ring
This is the most important part of the story where money is concerned. Even though the ring isn't "money" per se, it is wealth beyond measure (especially in considering what it represents: the one true religion). The ring appears when Nathan the Wise tells a story of three brothers. Their father is supposed to pass an heirloom ring to his "favorite" son. The father, who loves all of his sons equally, refuses. Instead, the father creates two duplicate rings.
If each of you received this ring straight from his father's hand, let each believe his own to be the true and genuine ring. Of this you may be sure: your father loved you all, and it was his ardent wish that all of you should love one another.
Each of the three brothers is given a ring and is asked for it to be treated as the original heirloom. The brothers are unable to figure out which is the "true" ring. (This is a metaphor for no one being able to decipher which is the "true" religion: Christianity, Islam, or Judaism.) Therefore, each brother lives the tradition as well as he can and knows that "a higher, greater court" will someday determine the true ring. In an ironic twist, the importance here draws us AWAY from money. The ring isn't important it all. It is what the ring SYMBOLIZES that is important: the one true religion that only God knows.
In conclusion, we need to understand that it is the parable of the ring that is the most significant "monetary" idea here. Three equal rings that stand for the three equal religions... only eventually will we find out what the true one is. And in an ironic twist, we learn that money is not as important as the values imparted here.