لَيَأْتِيَنَّ عَلَى النَّاسِ زَمَانٌ لَا يَبْقَى أَحَدٌ إِلَّا أَكَلَ الرِّبَا، فَإِنْ لَمْ يَأْكُلْهُ أَصَابَهُ مِنْ بُخَارِهِ
Translation: A time will come upon people when virtually everyone will encounter usury; even one who does not consume it directly will be touched by its vapor—that is, its indirect effects.
Source: أحمد وأبو داود
لَيَأْتِيَنَّ emphatically points toward a future time. الرِّبَا means usury. فَإِنْ لَمْ يَأْكُلْهُ introduces the case of someone not consuming it directly, while أَصَابَهُ مِنْ بُخَارِهِ pictures being touched by its indirect effects.
The moral lesson is vigilance concerning financial dealings in an environment where usury is widespread. Here “eat” is an Arabic idiom for benefiting from unlawful wealth, not literally chewing or swallowing it.