The purpose of religion is to know, serve, and love God. But you can only serve and love someone, if you know him or her. You cannot serve or love an invisible or unknown person. Only the Vedic scriptures describe exactly who the person God is. The non-Vedic scriptures don’t have a clue as to who God is. Serving and loving God includes serving and loving all the creatures of God. This means serving and loving all human beings and animals. We should not hurt or eat any of our brothers and sisters. The animals are also our brothers and sisters.
Being freed from attachments, fear, anger, and fully situated in thought of me, many have become purified by penance and knowledge of me. They all attained pure love for me.”Lord Krishna, Bhagavad-Gita 4.10
Can anyone love an unknown or invisible person? No. This can be proven by the fact that mothers kill their unborn and thus unseen child with abortion. How many mothers would kill their live (seen) child? It is only possible to love a known and visible person.
Mother Teresa of Calcutta, a Christian missionary, admitted towards the end of her life that she felt emptiness in her life. This was emptiness of God. One can read the non-Vedic scriptures for millions of years but will never be able to describe God, because they do not describe Him. Only the Vedic scripture describe God and in complete. Thus if one wants to know God and be religious, then one must read and follow the eternal Vedic scriptures.