Holy water is used in Christian baptism ceremonies across the world
Most people in the Christian tradition are familiar with holy water.
In Anglicanism, Catholicism, Eastern Orthodoxy and some other Churches, holy water is water which has been sanctified by a priest or bishop for the purpose of baptism and the blessing of persons, places, and objects.
Holy water is found in stoups at the doors of Catholic churches and some Anglican churches as well.
People dip their fingers in the holy water and make the sign of the cross when entering the church. This is a reminder of baptism.
But Christianity is not the only religion which sets great store by holy water.
Indeed, water with its power to cleanse, purify and slake the thirst has a particularly rich symbolic meaning in most religious traditions.
Holy water in Islam
Zam Zam water is sacred to Muslims and comes from a specific source in Saudi Arabia.
Suleman Nagdi, spokesperson for the Federation of Muslim Organisations, told me of the importance of this holy liquid.
He said that it is believed that the sacred well near Mecca from which the water comes has been flowing since the time of Abraham.
People on the Hajj pilgrimage almost invariably bring some water from the well back home with them.
"The majority of people will consume the water as normal water," Suleman explained. "Some believe it has medicinal qualities. Some people might sprinkle the water but this is rare"
Whatever the case, the water is considered very holy.
Zam Zam water is in the news as Ramadan gets under way, but not for any positive reason.
A health warning
Muslims in Leicestershire are being urged to avoid drinking bottled sacred water, which could be contaminated with arsenic.
Some tests on Zam Zam water sold in the UK has shown high arsenic levels
Under Saudi law, Zam Zam water cannot be exported from Saudi Arabia for commercial purposes and can only be imported for personal use.
So water on sale in the UK that is labelled as Zam Zam is of uncertain origin.
It will be illegal and probably not water authentically drawn from the Holy well in Mecca.
Colin Hoskins of Leicestershire County Council Trading Standards, said tests on some of this water sold in the UK indicate almost three times the legal limit of arsenic.
"We are coming up to the time of year when there might be more Zam Zam water around for sale in the shops [Ramadan]."
The penalty for selling false Zam Zam water is hefty.
Offenders face an unlimited fine or two years imprisonment and traders can face a fine of £20,000 or six months' imprisonment for selling water which is not safe.
Suleman Nagdi was emphatic that Zam Zam water should not be bought or sold and that cases of this happening should be reported.
I find all this very sad.
Bringing back Zam Zam water from Hajj, the once in a lifetime pilgrimage all Muslims try to make, is one thing.
Attempting to make a profit out of it or, even worse, ordinary water which has no connection with the holy well, is contemptible.
It profanes the sacred.