وَأَحَلَّ اللَّهُ الْبَيْعَ وَحَرَّمَ الرِّبَا
God has permitted trade and prohibited usury.
The words plainly establish permission for sale and prohibition of ribā. They also answer the claim that trade and ribā are equivalent. The passage was brought forward to distinguish their legal statuses, making it naṣṣ for that purpose.
Two indications:
1. Permission of sale and prohibition of ribā are apparent.
2. The rejection of treating them alike is the expressly intended point of the passage.
Context strengthens the indication of the intended purpose; it does not license arbitrary changes to the words.