Digha Nikaya 2:310
SUJATOIdha, bhikkhave, bhikkhu anuppannānaṁ pāpakānaṁ akusalānaṁ dhammānaṁ anuppādāya chandaṁ janeti vāyamati vīriyaṁ ārabhati cittaṁ paggaṇhāti padahati;
It’s when a mendicant generates enthusiasm, tries, makes an effort, exerts the mind, and strives so that bad, unskillful qualities don’t arise.