The Prophet ﷺ said, "No 'Adwa (no contagious disease is conveyed to others without Allah's permission), nor Tiyara, but I like the good Fal, i.e., the good word."  

عَنِ النَّبِيِّ ﷺ قَالَ لاَ عَدْوَى وَلاَ طِيَرَةَ وَيُعْجِبُنِي الْفَأْلُ الصَّالِحُ الْكَلِمَةُ الْحَسَنَةُ  

There is no transitive disease, no ill omen, no ghoul. Note: The majority of scholars interpret this to mean that these things in and of themselves do not transmit or cause harm through supernatural or hidden means but that Allah is ultimately in control and any fearful superstition around these is false. (Using translation from Muslim 2222a)   

قَالَ رَسُولُ اللَّهِ ﷺ «لَا عَدْوَى وَلَا طِيَرَةَ وَيُعْجِبُنِي الْفَأْلُ»