The roots of Christianity as a religion are in the Middle East, and it is a hot area where people tend to wear sandals. The roads were often dusty due to the dryness of the desert, and it was considered an honor to wash the feet of guests. Jesus Christ was said to have washed the feet of his disciplines before they joined him for the final supper before he was crucified, and it has been handed down as a religious practice in many Christian sects.
The modern ritual of washing of the feet has changed little from the past, and it is often considered an act of love by those who perform it. While it did begin as a secular tradition, it was carried into a religious ritual because it was performed by Jesus and on him. Noted in the Bible as a ritual, it has been a traditional part of Christianity that is still performed today.
The washing of feet is often done for the poor in the Roman Catholic religion, and it is a way to show them the love of God and the church. Done by church officials of all levels, it is celebrated on the Thursday before Easter each year. This marks the day of the Last Supper, and it also marks the command of Jesus to his disciplines to love one another.
There are now many different Christian religious institutions, and some of them also practice the rite of foot washing. Some follow the same ritual as the Roman Catholics, but others perform it on a regular basis during the year. There are congregations that will do it every few months, but some have dropped the practice over the years. Many of the religious institutions that still perform it will also have a mass to commemorate the Last Supper after the ritual.