Canto 2 -
Ayodhyā-kāṇḍa
Chapter 21: Rāma Consoles Kausalyā and Lakṣmaṇa
Text 2.21.6

न तं पश्याम्यहं लोके परोक्षमपि यो नरः।
स्वमित्रोऽपि निरस्तोऽपि योऽस्य दोषमुदाहरेत्॥

na taṁ paśyāmy ahaṁ loke parokṣam api yo naraḥ
sva-mitro ’pi nirasto ’pi yo ’sya doṣam udāharet

na = not; tam = a single; paśyāmi = have seen; aham = I; loke = in the world; parokṣam = in Rāma’s absence; api = even; yaḥ = who; naraḥ = man; sva-mitraḥ = if he is His friend; api = even; nirastaḥ api yaḥ = or has been criticized by Him; asya = of His; doṣam = of any fault; udāharet = has spoken.

I have not seen a single man in the world who even in Rāma’s absence has spoken of any fault of His, even if he is His friend or has been criticized by Him.

“What is the proof that Rāma is faultless?” Anticipating this question, Lakṣmaṇa notes here that there is not even an accusation [of Rāma being faulty]. Even His friends haven’t found fault with Him in His absence, what to speak of in His presence? This is also the case with His enemies. And they don’t do so even when criticized by Rāma for some offense.

Naraḥ indicates that Lakṣmaṇa is talking about human beings, not asuras.1 An asura might find fault [with Rāma]. 

1 He is also referring to human beings who are not affected by the asuras.