This verse (chaupai) is from the Balakanda chapter of Shri Ramcharitmanas.

लखि सुबेष जग बंचक जेऊ। बेष प्रताप पूजिअहिं तेऊ॥ उघरहिं अंत न होइ निबाहू। कालनेमि जिमि रावन राहू॥
This verse (chaupai) is found at the beginning of Balakanda, discussing the significance of satsang (association with the righteous).
Meaning : Even those who are deceivers, when they appear in good (saintly) attire, are honored by the world due to the power of their appearance. However, one day, they are inevitably exposed. Their deception cannot last forever, just as it happened with Kalanemi, Ravana, and Rahu.
Context: where this chaupai appears in Shri Ramcharitmanas
At the beginning of Balkand, Goswami Tulsidas describes the glory of saints and the nature of the wicked. He observes that impostors who put on the beautiful garb of a saint are also worshipped in this world because of that garb. But in the end their deceit is exposed and does not last, as happened with Kalnemi, Ravan, and Rahu.
Transliteration
Lakhi Subesh Jag Banchak Jeu. Besh Pratap Pujiahin Teu.. Ugharahin Ant Na Hoi Nibahu. Kalnemi Jimi Ravan Rahu..
Word meanings
- Lakhi = seeing
- Subesh = beautiful (saintly) garb
- Banchak = impostor, deceiver
- Besh pratap = by the power of the garb
- Pujiahin = are worshipped
- Ugharahin = are exposed
- Nibahu = lasting to the end
- Jimi = just as
As a Shalaka answer
This is a cautionary answer. What the matter or person appears to be on the surface is not what it is within, so do not trust appearances. Success is doubtful, so examine everything carefully before proceeding.