I'm spending it to get higher
Could mean one of two things, either:
Nas is spending his money to buy drugs such as marijuana to literally get “higher”, or more intoxicated..
Nas is spending his money in order to ascend into a luxurious, high-class lifestyle; thus he is buying expensive houses, cars, clothes, jewelry, etc. to fit his newly lavish lifestyle (“living the high life”)..
A third and most likely meaning, since it ties with the previous bar is that Nas is spending cash to get in good grace with god so he´ll go to heaven. Since in the previous line he said currency has made us believe in the messiah. You know how all churches takes fees for rich people to rid them their sins?
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