—to the congregation when a man entered and sat down. He said to him, "Have you prayed?" The man answered, "No." He replied, "Then stand and pray two rakʿahs." The Prophet ﷺ did not scold him for omitting the prayer, for it was possible that the man had already prayed and the Prophet simply had not noticed.
In the same way, if you see someone eating or drinking during the daytime in Ramadan, do not chastise him outright. First ask him, for he may have a legitimate excuse for breaking the fast. Say, "Why are you not fasting?" He might be traveling, or he might be suffering from an illness that requires frequent intake of water—kidney pain, for example, often demands copious drinking—even though to onlookers he appears perfectly healthy. The essential rule is that you must be sure a duty has indeed been abandoned before you command it, and equally sure that a wrong has truly been committed before you forbid it; otherwise a person may be innocent while you assume him guilty.
Consider another illustration: you notice a man in a car with a woman. She could be unrelated to him, but she could just as easily be one of his unmarriageable relatives or his wife. Therefore, do not denounce him until you know the reality of the situation. Circumstantial indicators might justify inquiry: suppose you sense something dubious about the man—behavior that a perceptive, intelligent observer would recognize. In that case you may approach and ask, "Who is this woman with you?" or "Why are you giving a ride to a woman who is not one of your unmarriageable kin?" What you may not do is automatically condemn every man you see walking with a woman or driving her in his car when you have no knowledge of whether any wrongdoing is taking place.