Majjhima Nikaya (Coleção dos Discursos Médios) 2:134
SUJATOiti ajjhattaṁ vā dhammesu dhammānupassī viharati, bahiddhā vā dhammesu dhammānupassī viharati, ajjhattabahiddhā vā dhammesu dhammānupassī viharati;
And so they meditate observing an aspect of principles internally …