Q: How is it possible that all the sins and so on from a deciple go to the guru, and the guru becomes sick? Is this true?
It is just a principle of karma that everyone involved in an activity gets some portion of the results.
This principle is even reflected in our conception of law. If several people conspired in different roles to execute a crime, for example, they are all punished for it – proportionate to the nature of their involvement.
Our parents, teachers, rulers, and even older friends and siblings strongly our decisions and actions. Therefore they also deserve some percentage of the punishment or reward we get for those decisions and actions. That is why the parents, gurus, kings, leaders and so on get some portion of the karma of the people who are in their care.
The guru doesn’t “take all the karma of a disciple.” If that were so, the disciple would disappear immediately from the karmic world! It is just that the guru accepts the responsibility of guiding the disciple’s actions. Whatever good or bad the disciple does has something (not everything, but something) to do with the quality of the guru’s guidance, and that is why the guru receives some (not all, but some) good or bad karma as a result of the disciples good or bad karmic actions.
It also works in bhakti. Krishna feels grateful to the guru for whatever sincere bhakti a disciple performs, because the guru is partially responsible for it. Conversely Krishna is personally displeased with a guru whose disciples perform aparādhā and otherwise work against the principles of pure devotion.
I hope this clarifies.
– Vraja Kishor das