Sangitisutta 3.1.112

3.1.112

So taṃ cittaṃ dahati, taṃ cittaṃ adhiṭṭhāti, taṃ cittaṃ bhāveti, tassa taṃ cittaṃ hīne vimuttaṃ uttari abhāvitaṃ tatrūpapattiyā saṃvattati.

They settle on that thought, stabilize it, and develop it. As they’ve settled for less and not developed further, their thought leads to rebirth there.