Canto 3 -
Araṇya-kāṇḍa
Chapter 39: Mārīca Describes his Second Encounter with Lord Rāma
Text 3.39.22

सोऽहं तवापराधेन विनश्येयं निशाचर।
कुरु यत्ते क्षमं तत्त्वमहं त्वा नानुयामि ह॥

so ’haṁ tavāparādhena vinaśyeyaṁ niśācara
kuru yat te kṣamaṁ tat tvam ahaṁ tvā nānuyāmi ha

saḥ aham = here I am; tava = your; aparādhena = due to offense; vinaśyeyam = about to perish; niśācara = O night-ranger; kuru =  do; yat = what; te kṣamam tat = are capable of; tvam = you; aham = [but] I; tvā = you; na = not; anuyāmi ha = will follow.

Here I am, about to perish, O night-ranger, due to your offense! Do what you are capable of, [but] I will not follow you.

So ’ham (“Here I am”) means “Here, I am, having become a saint.” Mārīca didn’t want to follow Rāvaṇa since he was sure that it would lead to a disaster.

In the next verse Mārīca states the reason [for him to conclude thus].