That’s easy. General welfare. The same clause they use for damn near every other social program and giveaway.
There are plenty of writings by Founding Fathers, those who wrote and supported the Constitution and its ratification - as well as early politicians where the ‘General Welfare’ clause is explained as not a grant to give away things/money, etc....but the very fact that a structured LIMITED GOVERNMENT provides the foundation of a people and a country that will benefit everyone.
Certainly that ‘general welfare’ clause has been abused to the point that its use destroys most of the rest of the Constitution. If the general welfare clause were to mean what the leftists thinks it means - the Bill of Rights would never have INCLUDED THE 9th and 10th Amendments.