.............taking away someone's rightful property, killing someone etc. or are those sins not included because they fall in the category of "Huququl ibad". if they are not being forgiven, then that is not the full forgiveness being guaranteed, is it?
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I think you said it, Haqooq ul ibad vs. haqooq Allah are the key terms here.
Violation of Haqooq ul ibad" can only be forgiven in one way. How? If you violate someone's property or life, you cannot be forgiven unless the person(s) impacted forgive(s) you. There are many options for that type of forgiveness that include: paying for the other party's loss+ other expenses (lawyer's fees, court cost etc.), or the aggrieved party may not ask for your money, but your time, or they may just forgive you.
isnt it interesting that religion always finds short cuts to reduce your sins? ...
In Islam that "BOGO" (By one get one free) type deals are reserved for worshiping aka Haqooq Allah. Yes Allah is Raheem and Kareem. He can give you double or triple or even higher reward for your worship.
If you as a clean shaven person say one namaz with best of intention, with clear heart, you may get double swab. While a Maulvi may not get the BOGO deal because his intentions or Niyyah was not good enough.
But these "special deals" don't come cheap either. You can't just do one Roza for the day Jews were saved and expect 365 days of equivalent worship. You must have a clean heart, no anti-semitism in your mind, and no hatred in your body then only then you may get some multiples of your worship.
However noone but Allah knows how pure your worship is. And this discussion should be looked at from that POV.