Hello Safaa, Here 'the devil' refers to Shylock. It means that the devil could use artful tricks quoting scripture and misinterpreting it in ways, that render his immoral acts reasonable; warrant or substantiate .

In this scene, Shylock uses a biblical reference when discussing a loan of money for Antonio. Antonio is very aware that the only one who will truly gain from the deal is Shylock. With this comment, Antonio is saying that anyone - even the devil himself - can quote(cite) holy scripture to justify their own selfish wants.

"The devil can cite Scripture for his purpose" Meaning: Bad people can appear to be good to achieve their objective. or even good things can be twisted to achieve bad ends. Origin: Spoken by Antonio in "The Merchant of Venice", written by William Shakespeare (1564-1616): Mark you this, Bassanio, The devil can cite Scripture for his purpose. An evil soul producing holy witness Is like a villain with a smiling cheek, A goodly apple rotten at the heart: O, what a goodly outside falsehood hath!