शत्रोः enemy, सकाशात् from the camp, सम्प्राप्तः having come, विभीषण: Vibheeshana, सर्वथा: in every way, शङ् क्या: doubtful, एवहि: surely, सहसा: suddenly, विश्वासयोग्यः worthy to be trusted, नकर्तव्यः not to be.

"Since he has come from the enemy's camp suddenly, surely Vibheeshana is to be suspected in every way. He is not worthy to be trusted."