Why is tilak applied on the forehead in a religious ceremony?
A tilak is an ornamental or religious mark on the forehead, also called tika. According to Hindu religious texts, applying tilak or tika is necessary at all religious ceremonies, without which no Hindu ceremony is complete. From birth till death tilak is a part of life. All gods, goddesses, yogis, saints, sages and mahatmas apply tilak on their forehead. Some householders also apply tilak daily, although generally it is customary to apply tilak at the beginning of the religious ceremony.
According to tradition, applying tilak is a symbol of honour being extended to the person. Guests are welcomed or seen off with tilak. Even when householders leave on long travel or 56 pilgrimage, they are seen off with a tilak and good wishes.
In the Brahmvaivartpuran, Brahmparv, 26, it is said:
If tilak is not adorned on the forehead at the time of a holy bath, yagya, prayer or religious ceremony, the effort bears no fruit. The Brahmin priest must have a tilak when performing prayers, tarpan and other ceremonies.
The Skandpuran explains with what fingers tilak must be applied for best results: