«وَهِيَ الْجَمْعُ بَيْنَ الْمُتَضَادَّيْنِ»
“Correspondence, also called ṭibāq or opposition, joins two contrary meanings.”
The principal condition is semantic opposition, not merely the presence of two words labelled antonyms in a dictionary. Some contrasts are established by polarity or by context.
The rhetorical effect arises when each side illuminates the other. The contrast should serve the intended statement rather than being inserted only for ornament.