Why should we chant 16 rounds ? what pleasure Krishna derives from it?

The chanting of the maha-mantra is to purify ourselves so we can become eligible to go to Goloka. In this struggle for material existence, we need something to connect us back to Krsna, something that is very powerful and will not be broken by Maya. Of course, nothing material fits the description - so we turn to something spiritual. Krsna is the Supreme Personality of Godhead, so he is all powerful, but only the names of Krsna are more powerful and more merciful than Krsna. Thus we take shelter of the Mahamantra to keep us afloat while we journey around this material ocean of birth and death.

Since we are constantly thinking about Krsna and remembering Krsna and chanting Krsna's name, this is the pleasure Krsna gets, because you are reciprocating the affection Krsna has for you.

Think about it this way - if a child's first word is "Mommy" or "Daddy" ... and he/she continues to say that word over and over... the Mother or Father isn't going to be annoyed and tell the child to be quiet... rather they get even more happy as the child continues to repeat that word. So in this sense, Krsna becomes very excited when you chant the Mahamantra, because you are calling out to Him.

I was looking around for something interesting things to share and came across this:

"Srila Prabhupada says, "The Krsna consciousness movement prescribes sixteen rounds daily because people in the Western countries cannot concentrate for long periods while chanting on beads. Therefore the minimum number of rounds is prescribed. However, Srila Bhaktisiddhanta Sarasvati used to say that unless one chants at least sixty-four rounds of japa (one hundred thousand names), he is considered fallen (patita).  According to his calculation, practically every one of us is fallen, but because we are trying to serve the Supreme Lord with all seriousness and without duplicity, we can expect the mercy of Lord Sri Caitanya Mahaprabhu, who is famous as patita-pavana, the deliverer of the fallen."

- See more at:http://harekrishnajapa.com/why-chant-16-rounds/#sthash.PMR9kjyn.dpuf"

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