1. Akrityanancha karanam and krityaanam varjanam (doing what is not to be done and not doing what is to be done) is sin as per dharma.
2. The reverse is punyam.
Vaishnavites believe both are to be detested and kept away from. The two together is called karma and karma binds a jeeva to prakriti for ever. In Tamil it is called "கடுவினைகள் இரு வினையும்". To get free from from these two tags, surrender to God is the way.
I beg to differ from that point.
Actions themselves are neither Papa or Punya.
Like Renukaji said it is motive behind the action which can be termed Papa or Punya.
For example Killing someone to get their wealth may be termed Immoral, illegal etc, but the same killing in the defence of one's country or in self defence can not be termed immoral and not illegal.
Krishna urges Arjuna to Kill.
Right action, Krishna states, "comes from the Supreme Spirit who is one, wherefore the all-pervading Spirit is at all times present in the sacrifice." The key to right action is detachment and disinterest in results. (Gita, pp. 24-5).
Punya is an act of apparent good, done by us inorder to gain a place in the temporary and inferior comforts of svarga and such The one who is interested in
the Ultimate Repose (Parama Dhaama) does not care about Punya. He just does his work as it is his duty and leaves the calculations of Punya and Paapa to the Lord.
Finally Chitra Gupta and Yama and his Naraka are all allegories. Yama (ja) means twin. Chitra Gupta is the chitta, the recalling mode of Mana. They do not exist separately. they exist with in us and torture us for our deeds. A Paapi suffers by his concience; and that is the combination of Yama, Chitra Gupta and Naraka.
Any action to fulfil our desires is sin (paap), but if it is for the benefit of others then virtue (punya).
Actions themselves have no papa or punya attached to it.
Most of the smrithis (manu smrithi in particular) is like the constitution, a book of laws. So it is time and place bound.
They are changeable (just as any constitution is).
