Some devotees find the study of Shastras as a means of liberation to be very difficult but it is not easy either to attain liberation through faith alone. Do not believe in depending on mere faith.
Though faith is basically pure, it becomes tainted when it befalls the lot of creatures, because creatures are naturally constituted from the three attributes (sattva, rajas and tamas) due to the power of the timeless Maya. When two attributes become weak and the third becomes strong, the natural tendencies of an individual are moulded according to that attribute. The mind is moulded according to the natural tendencies, actions follow the mind, and the individual takes rebirth according to the karmas, the accumulated effect of actions.
Just as a seed disappears to create a tree and tree gets incorporated later in the seed and the species of the tree does not disappear even after millions of aeons of this cycle, similarly even when a creature is reborn countless number of times, there occurs no change in the three attributes. The faith which has come to the lot of a creature is therefore according to these attributes. If Sattva attribute increases it leads to acquiring of knowledge but it is opposed by the other two attributes. Pure faith based on Sattva attribute fructifies into liberation, but how will the Raja and Tama attributes remain quiet? When Raja attributes overrides the Sattva attribute then the faith (which is now tainted by the Raja attribute) sweeps together the karmas. And when the Tama attribute becomes strong the faith breaks down and entangles the creatures in all sorts of sense-pleasures. Thus Arjuna, the faith cannot be separated from the three attributes therefore the faith is qualified by the three attributes Sattva, Raja and Tama.
Water is the essence of life but it becomes fatal if mixed with poison, pungent if mixed with pepper and sweet if mixed with sugarcane juice. Similarly, when Tama attribute increases, the creature that dies and is reborn acquires a faith that is Tamasic i.e. tainted by the Tama attribute. Thus the faith of a Tamasic creature is Tamasic. Similarly the faith of a Rajas (i.e. one tainted by Raja attribute) creature is Rajas and a Sattvic creature Sattvic (i.e. one tainted by Sattva attribute). Thus this structure of the universe is constituted from faith. But you should understand the impressions of the three attributes on it. Just as one can recognise the nature of the past Karmas of a person from his condition in this life, similarly there are signs that can indicate the three different forms of faith.