Why only ghee prepared from cow's milk should be used?
Generally any oil lamp emits frequencies consisting of raja particles but the sesame oil emits some sattvafrequencies also. Therefore the lamp with sesame oil is comparatively more sattvik. However the ghee lamp emits the sattvik frequencies in maximum amount compared to any oil lamp. Here we have to remember one thing that it is useful use ghee prepared only from the cow’s milk in the lamp lit in front of Deity. This is because in such ghee the Deites’ principles are already existent. Such a ghee which is dominant in sattva component emits luminous figures in the atmosphere. Such luminous figures are forms of Tej tattva or absolute fire element. Thus even though the use of ghee is recommended because of its capacity to emit maximum sattva frequencies, we can use sesame oil lamp if the use of ghee is not possible because of financial restraints or otherwise.
Now let us see the points to be noted while actually using a lamp.
Do not kindle an oil lamp with a ghee lamp and vice versa
Do not kindle one lamp with another similar lamp. For example if there are two niranjans (a type of lamp) in anarti platter then do not light one niranjan with another niranjan. Similarly do not light one pillar of lamps with another.
Sometimes while performing puja we unknowingly touch the lamp. We should immediately wash our hands then. This is because when we worship a deity the sattva component of the lamp increases. When we touch the lamp the raja-tama particles from our body enter the lamp by way of touch. This reduces the purity of the lamp. The water has the property of encompassing everything. Anything which is offered to a deity through the medium of water reaches Him/Her faster. When we wash our hands we are one way dissolving our sins in the water. The spiritual practice of water is to assimilate in itself sins done by all. The extremely merciful Deities absolve us from our defects when we offer them at their feet through the medium of water.