Trung Bộ Kinh (Majjhima Nikaya) 3:124
SUJATOdhammesu dhammānupassī viharati ātāpī sampajāno satimā vineyya loke abhijjhādomanassaṁ, upaṭṭhitāssa tasmiṁ samaye sati hoti asammuṭṭhā.
principles, at that time their mindfulness is established and lucid.