In Ramayana, we see that Ravana took the form of a Sadhu to take away Seeta.

The brave and powerful king that he was, Ravana could have come in his original form to take Seeta away, as Seeta was there alone. Why did he have to come in the garb of a Sadhu?

Ravana bore a curse that the moment he touched a woman with lewd intentions, his head would burst into a thousand pieces.
Only a Sanyasi is free from the feelings of lust. Hence Ravana comes in a Sanyasi’s attire to take away Seeta.