Dutiyanidānasutta
“Tīṇimāni, bhikkhave, nidānāni kammānaṁ samudayāya. Katamāni tīṇi? Atīte, bhikkhave, chandarāgaṭṭhāniye dhamme ārabbha chando jāyati; anāgate, bhikkhave, chandarāgaṭṭhāniye dhamme ārabbha chando jāyati; paccuppanne, bhikkhave, chandarāgaṭṭhāniye dhamme ārabbha chando jāyati. Kathañca, bhikkhave, atīte chandarāgaṭṭhāniye dhamme ārabbha chando jāyati? Atīte, bhikkhave, chandarāgaṭṭhāniye dhamme ārabbha cetasā anuvitakketi anuvicāreti. Tassa atīte chandarāgaṭṭhāniye dhamme ārabbha cetasā anuvitakkayato anuvicārayato chando jāyati. Chandajāto tehi dhammehi saṁyutto hoti. Etamahaṁ, bhikkhave, saṁyojanaṁ vadāmi yo cetaso sārāgo. Evaṁ kho, bhikkhave, atīte chandarāgaṭṭhāniye dhamme ārabbha chando jāyati. Kathañca, bhikkhave, anāgate chandarāgaṭṭhāniye dhamme ārabbha chando jāyati? Anāgate, bhikkhave, chandarāgaṭṭhāniye dhamme ārabbha cetasā anuvitakketi anuvicāreti. Tassa anāgate chandarāgaṭṭhāniye dhamme ārabbha cetasā anuvitakkayato anuvicārayato chando jāyati. Chandajāto tehi dhammehi saṁyutto hoti. Etamahaṁ, bhikkhave, saṁyojanaṁ vadāmi yo cetaso sārāgo. Evaṁ kho, bhikkhave, anāgate chandarāgaṭṭhāniye dhamme ārabbha chando jāyati.
Sources (2nd)
“Mendicants, there are these three sources that give rise to deeds. What three? Desire comes up for things that stimulate desire and greed in the past, future, or present. And how does desire come up for things that stimulate desire and greed in the past, future, or present? In your heart you think about and consider things that stimulate desire and greed in the past, future, or present. When you do this, desire comes up, and you get attached to those things. This lust in the heart is what I call a fetter. That’s how desire comes up for things that stimulate desire and greed in the past, future, or present.