Bhagavad Gita 15.11यतन्तो योगिनश्चैनं पश्यन्त्यात्मन्यवस्थितम्।यतन्तोऽप्यकृतात्मानो नैनं पश्यन्त्यचेतसः ॥

The description of the evolution of the individual soul is now complete.The Yogins who strive with an iron determination, fiery resolve, faith, earnestness and wellbalanced mind, see Him established in their hearts. They behold Him dwelling in their own mind or intellect. They recognise Him -- This I am. But those who are of full intellect and without proper discipline of the mind and the senses, who have not been purified by austerity, selfless service and charity, who have not subdued their senses, who have not practised regular meditation, who have not given up their evil ways, who have not eradicated lust, pride, egoism, anger, greed and hypocrisy, who have not developed true discrimination between the Real and the unreal, however hard they may struggle to know Him by means of the study of the sacred scriptures, do not behold Him. They are not able to attain Selfrealisation. Mere study of scriptues alone cannot help one who has an impure mind to attain Selfrealisation. The aspirant should have a calm and pure mind. He should practise constant, protracted and profound meditation on the Self