(Kadamba Kanana Swami, 29 September 2013, Melbourne, Australia, Srimad Bhagavatam 2.2.36)
When we engage in pious activities, the result is that our consciousness becomes pious and then our thoughts and our actions become pious. When we engage in purifying activities then gradually the result is that our consciousness changes, obviously. It is said,
In the Padma Purana, it is stated that there is aprārabdha-phalaṁ within the heart – unmanifest karma. Many reactions and too many activities are stored within the heart, and the result is that these are like seeds that are within the heart (bījaṁs). These bījaṁs create a particular inclination. So, because we have so many past sinful activities, there are so many sinful bījaṁs within the heart and therefore, the inclination towards sin is there and therefore, there are thoughts which are sinful.
Fortunately, it is mentioned in the Srimad Bhagavatam, in the chapter where Maharaja Pariksit is stopping kali from entering the kingdom, at that point, there is a purport which mentions that thoughts in the age of kali are free – you can think whatever you like and there is no reaction. That is a bit of relief. Let us be frank, I mean sometimes what comes into the mind!? We killed a few people! What to do? It happens. There is a bad driver for example. What to do and what not to do; and so many other things may happen within the mind but fortunately, there are no reactions for thinking it. But of course, if we contemplate sinful activities then it may lead to sinful actions,
dhyāyato viṣayān puṁsaḥ
saṅgas teṣūpajāyate, (Bhagavad-gita 2.62)
Because contemplation causes attachment and then from the attachment comes the desire to act.