The case is Busser v. Snyder, 282 Pa. 440, 128 A. 80 (Pa. 1925). The law is cited as the "Old Age Assistance Act of May 10, 1923, P. L. 189", but I could not find the text of the act. The court case explains that it established a pension of up to one dollar per day for residents over the age of seventy having annual income below $365 and assets below $3000.
The provision of the [Pennsylvania] Constitution under which the act was declared void [by the lower court] reads as follows: "No appropriations, except for pensions or gratuities for military services, shall be made for charitable, educational or benevolent purposes, to any person or community, nor to any denominational or sectarian institution, corporation or association."
And the Pennsylvania Supreme Court agreed. They also distinguished it from other laws that remained constitutional:
Laws to assist the poor and indigent were still constitutional. The state argued that the Old Age Assistance Act fell in that category, but the court held that the income and property limits were not a reasonable definition of "poor", especially since the law would pay pensions to people even if they were able to work.
The state apparently had a retirement pension system for public employees. This was also held to be different in that it was delayed compensation for employees, in exchange for the service they performed, and thus not charitable or benevolent.