The case of First Methodist Church of San Leandro et al. v. Horstmann, Assessor of Alameda County, California et al., 1957 revolved around the issue of property tax exemptions for religious institutions. The First Methodist Church in San Leandro had purchased a piece of land with the intention to build a church on it but was unable to do so due to financial constraints and instead rented out portions for commercial use while retaining some parts for religious activities like Sunday school classes and meetings. However, the county assessor levied taxes on this property arguing that since it was not exclusively used for religious purposes as required by state law, it did not qualify for tax exemption. The Supreme Court ruled in favor of the church stating that even though part of the property was being commercially leased out temporarily due to financial necessity, its primary purpose remained religion-oriented which made it eligible for tax exemption under California law.

In the dissenting opinion for the case of First Methodist Church of San Leandro et al. v. Horstmann, Assessor of Alameda County, California et al., Justice Frankfurter argued against the majority's decision to dismiss the appeal for lack of a substantial federal question. He contended that there was indeed a significant constitutional issue at stake concerning religious freedom and equal protection under law as guaranteed by Fourteenth Amendment. The church property in question had been denied tax exemption on grounds that it was not being used exclusively for religious worship but also rented out part-time to secular organizations - an arrangement common among many churches nationwide due to financial necessity. To penalize such practice with taxation would disproportionately burden smaller or less affluent congregations who rely more heavily on rental income, thus potentially infringing upon their free exercise rights and violating principles of equality before law.