When thomas jefferson received the treaty for the louisiana purchase, he

Jefferson was uncertain as to whether he had constitutional authority to accept the treaty.

Thomas Jefferson was a "strict constructionist."  In other words, he believed that we ought only do what is strictly outlined in the Constitution.  Loose constructionists, by contrast, believed that we are free to take an action if that action is not specifically prohibited by the Constitution.

Because of Jefferson's views on how to interpret and abide by the Constitution, it's no surprise that he had some hesitancy about proceeding with the Louisiana Purchase.  He thought the matter should be brought to the American people for them to approve a constitutional amendment.  However, others in government didn't view the matter the same way, and eventually the treaty was ratified.

The treaty, as negotiated by James Monroe and Robert Livingston on behalf of the USA, was announced on July 4, 1803.  The Senate ratified the treaty in October, 1803, after disregarding President Jefferson's draft for an amendment to the Constitution.