You're not going to find the law in the original Constitution because it was left to each state to decide:
Eventually, the framers of the Constitution left details of voting to the states. In Article I Section 4, the Constitution says:
The times, places and manner of holding elections for Senators and Representatives, shall be prescribed in each state by the legislature thereof; but the Congress may at any time by law make or alter such regulations.
Unfortunately, leaving election control to individual states led to unfair voting practices in the U.S. At first, white men with property were the only Americans routinely permitted to vote. President Andrew Jackson, champion of frontiersmen, helped advance the political rights of those who did not own property. By about 1860, most white men without property were enfranchised. But African Americans, women, Native Americans, non-English speakers, and citizens between the ages of 18 and 21 had to fight for the right to vote in this country.
Library of Congress: The Founders and the Vote
By "routinely permitted to vote", they mean that it's true in general but not in every case. In particular, some women and African Americans could vote in New Jersey before 1807 if they met certain requirements:
The 19th Amendment gave women the right to vote, but some New Jersey women could vote as early as 1776. New Jersey’s first constitution in 1776 gave voting rights to “all inhabitants of this colony, of full age, who are worth fifty pounds … and have resided within the county … for twelve months.” In 1790 the legislature reworded the law to say “he or she,” clarifying that both men and women had voting rights. But only single women could vote because married women could not own property. Still, many unmarried women voted in New Jersey in the 1790s and the very early 1800s.
African Americans in the state could vote if they met the residency and property requirements. In 1797, the New Jersey government required voters to be free inhabitants. We do not know if enslaved African Americans voted before this law was passed -- the property requirements made that unlikely, but no law specifically prohibited them from doing so.
Did You Know: Women and African Americans Could Vote in NJ before the 15th and 19th Amendments?