user533: I would like to know if, in the pali canon, there is any practice for purifying karma, such as: Using mantras, prostrations etc...
I know there is the concept of using good Karma, like dana, to balance the results (vipaka) of bad Karma, however the question is focused on rituals or practices.

user106: In Sutta Nipata there is a lyric about if and when the Buddha gets approached by the question of earning merits (which in my thoughts appear when I read of "polishing karma"). I've kept this to my "personal inventary" long time ago; moreover it reminds me also of the demand of general wide-heartedness of any follower that the Buddha was going to accept... 
see: Palicanon Thansissaro Bhikkhu , Pali 

(english by Thanissaro Bhikkhu)
SN III,2 Padhana Sutta
(...)
Saying these verses, Mara stood in the Awakened One's presence.
  And to that Mara, speaking thus, the Blessed One said this:
"Kinsman of the heedless, Evil One, come here for whatever purpose:
I haven't, for merit, even the least bit of need.
Those who have need of merit: those are the ones Mara's fit to address.
In me are conviction, austerity, persistence, discernment.
Why, when I'm so resolute do you petition me to live?
  (...)


user43: As I pointed out in "If I undergo suffering now, will my next birth be better?" a while ago, liberation is not attained by "burning" past karma, but through "abandoning of unskillful mental qualities and the attainment of skillful mental qualities in the here-&-now"
As @Yam Marcovic showed in his "large boulder" quote (SN 42.6), Buddha of Pali Canon laughed at using rituals to improve someone else's rebirth. Indeed, how can your chanting help a dead person attain skillful mental qualities?! :)
However, Buddha never denied efficacy of rituals for changing one's own mood and motivation. In fact Buddha promoted usage of verbal aids for attainment of first jhana, and mantras can be seen as a kind of verbal aid.
In Tibetan Buddhism mantras and prostrations are used to cleanse one's own mind (not past karma!), one's own habitual tendencies. Specifically, mantras help stop inner dialog, and prostrations help against egoistic resistance.
From Mahayana perspective, denying efficacy of such self-directed rituals is foolish, because rituals obviously do change mood and motivation of the performer and participants.

533: <p>I would like to know if, in the pali canon, there is any practice for purifying karma, such as: Using mantras, prostrations etc...</p>

<p>I know there is the concept of using good Karma, like dana, to balance the results (vipaka) of bad Karma, however the question is focused on rituals or practices.</p>
 106: <p>In Sutta Nipata there is a lyric about if and when the Buddha gets approached by the question of <em>earning merits</em> (which in my thoughts appear when I read of "polishing karma"). I've kept this to my <em>"personal inventary"</em> long time ago; moreover it reminds me also of the demand of general <strong><em>wide-heartedness</em></strong> of any follower that the Buddha was going to accept... </p>

<p>see: Palicanon <a href="http://www.accesstoinsight.org/tipitaka/kn/snp/snp.3.02.than.html" rel="nofollow">Thansissaro Bhikkhu</a> , <a href="http://www.palikanon.com/pali/khuddaka/sn/sn_iii02-3_456.htm" rel="nofollow">Pali</a> </p>

<blockquote>
  <p><em>(english by Thanissaro Bhikkhu)</em></p>
  
  <p><strong><em>SN III,2 Padhana Sutta</em></strong></p>
  
  <p>(...)</p>
  
  <p>Saying these verses, Mara stood in the Awakened One's presence.<br>
  And to that Mara, speaking thus, the Blessed One said this:<br>
  <em>"Kinsman of the heedless, Evil One, come here for whatever purpose:</em><br>
  <strong><em>I haven't, for merit, even the least bit of need.</em></strong><br>
  <em>Those who have need of merit: those are the ones Mara's fit to address.</em></p>
  
  <p><em>In me are conviction, austerity, persistence, discernment.</em><br>
  <em>Why, when I'm so resolute do you petition me to live?</em><br>
  (...)</p>
</blockquote>
 43: <p>As I pointed out in "<a href="https://buddhism.stackexchange.com/a/1672/43">If I undergo suffering now, will my next birth be better?</a>" a while ago, liberation is not attained by "burning" past karma, but through "abandoning of unskillful mental qualities and the attainment of skillful mental qualities in the here-&amp;-now"</p>

<p>As @Yam Marcovic showed in his "large boulder" quote (<a href="http://www.accesstoinsight.org/tipitaka/sn/sn42/sn42.006.than.html" rel="nofollow noreferrer">SN 42.6</a>), Buddha of Pali Canon laughed at using rituals to <em>improve someone else's rebirth</em>. Indeed, how can your chanting help a dead person attain skillful mental qualities?! :)</p>

<p>However, Buddha never denied efficacy of rituals for changing <em>one's own</em> mood and motivation. In fact Buddha promoted usage of verbal aids for attainment of first jhana, and mantras can be seen as a kind of verbal aid.</p>

<p>In Tibetan Buddhism mantras and prostrations are used to cleanse <em>one's own mind</em> (not past karma!), <em>one's own</em> habitual tendencies. Specifically, <strong>mantras help stop inner dialog, and prostrations help against egoistic resistance</strong>.</p>

<p>From Mahayana perspective, denying efficacy of such self-directed rituals is foolish, because rituals obviously do change mood and motivation of the performer and participants.</p>
