كَادَ الْفَقْرُ أَنْ يَكُونَ كُفْرًا
Poverty may bring a person close to disbelief.
Source: البيهقي
كَادَ means “nearly” or “came close to.” الْفَقْرُ means poverty and كُفْرًا means disbelief. The warning does not mean every poor person becomes an unbeliever. Severe hardship can expose some people to despair, resentment, or wrongful choices.
In كَادَ الْفَقْرُ أَنْ يَكُونَ, كَادَ is a special incomplete verb; الْفَقْرُ is its subject, and أَنْ يَكُونَ introduces what the state may approach. The grammar conveys a danger, not an inevitable result.