Although a person may have some immoral habits due to his past association, if he is engaged fully in Krishna consciousness, these habits are not to be considered important. Whatever the case, if one becomes Krishna conscious, he will gradually be purified and will become a sadhu. As one progresses in executing Krishna consciousness, his bad habits diminish, and he attains to saintly perfection.
In this regard there is the story of a thief who went on a pilgrimage to a holy town, and on route he and the other pilgrims stopped to rest overnight at an inn. Being addicted to stealing, the thief began making plans to steal the other pilgrims’ baggage, but he thought, “I’m going on a pilgrimage, so it doesn’t seem appropriate that I should steal this baggage. No, I shall not do it.” Nonetheless, due to his habit, he could not keep his hands off the baggage. So he picked up one person’s bag and placed it in another place, and then another person’s bag and placed it elsewhere. He spent all night placing different bags in different places, but his conscience bothered him so that he could not take anything from them. In the morning, when the other pilgrims awoke, they looked around for their bags and couldn’t find them. There was a great row, and eventually, one by one, they began to find the bags in various places. After they were all found, the thief explained: “Gentlemen, I am a thief by occupation. Being that I am habituated to stealing at night, I wanted to steal something from your bags, but I thought that since I am going to this holy place, it is not possible to steal. So I may have rearranged the baggage, but please excuse me.” This is the characteristic of a bad habit. He does not want to commit theft anymore, but because he is habituated, sometimes he does. Thus Krishna says that one who has decided to refrain from his immoral habits and make progress in Krishna consciousness is to be considered a sadhu, even if out of past habit or by chance he yields to his fault. In the next verse we find that Sri Krishna says:
“He quickly becomes righteous and attains lasting peace. O son of Kunti, declare it boldly that My devotee never perishes.” (Bg. 9.31)
Because one has committed himself to Krishna consciousness, it is proclaimed here by Sri Krishna that within a very short time he will become saintly. One may pull the plug out of an electric fan, and the fan may still go on even though the juice has been disconnected, but it is understood that the fan will soon come to a stop. Once we take shelter of the lotus feet of Krishna, we turn the switch off for our karmic activities, and although these activities may still revolve, it is to be understood that they will quickly diminish. It is a fact that whoever takes to Krishna consciousness does not have to endeavour independently to become a good man. All the good qualifications will automatically come. It is stated in Srimad-Bhagavatam that one who has attained Krishna consciousness has simultaneously attained all good qualities. On the other hand, if a person is devoid of God consciousness and yet has many good qualities, his good qualities are to be considered useless, for he will not in any way be prohibited from doing that which is undesirable. If one is devoid of Krishna consciousness, he is sure to commit mischief in this material world.
Ref >> Srila Prabhupada Vani.