Among the people there is one whose speech fascinates you in this worldly life; he may even call upon Allah to witness what is in his heart, yet he is your staunch opponent.
Meaning:-
fascinates: to attract and hold attentively by a unique power
Staunch: someone who is firm, loyal, and steadfast in their beliefs, faithful, support for a cause or individual
Simplified Breakdown:- Describes those who are hypocrites, impressing others with their talk about worldly matters and swearing by Allah as if they are sincere, but in reality they are enemies and saboteurs of the faith.
Meaning:-
saboteurs: a person who destroys or damages something deliberately.