AN6.45
Karma is like debts and interests that accumulate
This sutta was also read out in the reading of MN65 Bhaddali Sutta by Ajahn Dhiravamso at around 8 minutes 35 seconds : http://media.bswa.org/sutta_study/Dhiravamso_2008_11_23.mp3
The hiriottappa parts of MN65 was also referred to in AN6.45.