Situated close to the door of any Catholic church you will find an open bowl, dish or container of holy water (although few are as impressive as ours – it is the original baptismal font from when the church was built and is VERY heavy). It is the custom when entering or leaving the church to dip one’s fingers in the water and to make the Sign of the Cross. This is done to remind the person of the cleansing from sin that they received at their own baptism. When the holy water is removed following the Mass of the Lord’s Supper and the stoup stands empty during the Sacred Triduum it is surprising how many people will still try to dip their fingers out of habit.
The custom of having holy water by the door of the church goes back to the middle ages at least and may be far older. Water mixed with salt was used in pagan Roman ceremonies as well as in Jewish ones and there is little doubt that the early Christians took over its use from such customs. The difference was that the water for Christian use had been prayed over. We know of prayers for the blessing of water in the east from the third century and special mention is made of water being blessed so that it might cure illness.
In both the eastern and the western churches the custom developed of washing ones hands before praying – something again having its origins in Roman and Jewish traditions of ritual purity. Basins for this purpose were provided by the entrances to churches from at least the fourth century although the water in them had not been blessed. The clergy would also wash their hands before the service and during it (the washing of the priest’s is a reminder of this). It is possible that the laity would wash their hands before receiving the Blessed Sacrament. This became less important as the change from receiving in the hand was replaced by receiving on the tongue but the holy water remained as a form of ritual cleansing.