The first Rashi in Pekudei explains why there is yet another parsha dealing with the Mishkan and its keilim. This parsha enumerates all the donations and shows how all the money was used. Rav Wolbe (Shiurei Chumash) cites the Medrash (Shemos Rabba 51, 1) which explains the pasuk (Mishlei 28, 20), "An honest man will increase blessing" as referring to Moshe. Moshe was able to account for every donation given toward the building of the Mishkan down to the last penny. Due to his unwavering integrity, the money he was entrusted with benefitted from Hashem's blessing, and it was exactly sufficient for the needs of the Mishkan. Moreover, the Medrash continues, when Moshe would count the yearly donations to the Mishkan he would wear a special garment that had no pockets thereby leaving no room for suspicion.
It is interesting to note that just as Sefer Shemos ends with the monetary integrity of Moshe Rabbeinu, likewise, it begins with the monetary integrity of his mother Yocheved. When Moshe was three months old and his mother could no longer hide him, she put him in a bassinet and placed it in the reeds on the banks of the river. The Torah tells us that the bassinet was made out of gomeh - cane. Being that Yocheved was trying to protect her son, it would have made more sense to build the bassinet out of strong sturdy cedar wood as opposed to cheap soft cane. The Gemara (Sotah 12a) infers from this incident that righteous people show more care regarding their money than they show regarding their bodies!
What do Chazal mean? Why do the righteous care so much about their monetary possessions? They are so careful with their money because every penny was earned honestly (ibid.). They don't steal and they don't cheat and therefore every dollar they receive is Heavenly ordained. If Hashem decided to entrust them with the money then obviously it was given to them for a purpose. Yocheved was extremely careful how she earned her money and therefore she was extremely careful how she used her money. She determined that a bassinet made out cane would suffice, and therefore, she did not want to use heaven sent money on an unnecessary expensive material.
To a certain extent many of us have lost this sensitivity toward money. We might forget something somewhere and decide that it is simply not worth going back for it. If Yaakov Avinu felt it imperative to expend the effort to retrieve some small bottles, shouldn't we at least be careful with expensive items that were forgotten? After all, if this is the money that Hashem has entrusted us with, we should do our best to protect it.
If one is careless with his money, says Rav Wolbe, sometimes it might be an indication that it was not earned honestly and therefore he doesn't appreciate the money as having come from Hashem. If we realize that our money was given to us to be used in our avodas Hashem, it might revolutionize the way we spend our money!