The other kind of distinction between sankhara and kammabhava is based on impulse moments. It is said that an act of murder or alms giving involves seven impulse moments. The first six impulse moments are called sankhara while the last is termed kammabhava.
The last method of classification is helpful when we speak of good deeds in rupa and arupa spheres. All the three methods apply in the case of good or bad acts in sensual world, but the first method is most illuminating for those who are not well informed.
Alternatively, Visuddhimagga attributes rebirth to flash backs, visions and hallucinations that hold a dying persons attention at the last moment of his life. So according to this commentary, kammabhava may be defined as the volition (cetana) that motivated his good or bad acts in the past and the sankhara as the mental state conditioned by his death bed experiences.