When Messenger of Allah ﷺ fell ill, Gabriel used to recite this: "In the name of Allah, may He cure you from all kinds of illnesses and safeguard you from the evil of a jealous one when he feels jealous and from the evil influence of eye."  

عَنْ عَائِشَةَ زَوْجِ النَّبِيِّ ﷺ أَنَّهَا قَالَتْ كَانَ إِذَا اشْتَكَى رَسُولُ اللَّهِ ﷺ رَقَاهُ جِبْرِيلُ قَالَ بِاسْمِ اللَّهِ يُبْرِيكَ وَمِنْ كُلِّ دَاءٍ يَشْفِيكَ وَمِنْ شَرِّ حَاسِدٍ إِذَا حَسَدَ وَشَرِّ كُلِّ ذِي عَيْنٍ  

Muhammad, have you fallen ill? Thereupon he said: Yes. He (Gabriel) said: "In the name of Allah I exorcise you from everything and safeguard you from every evil that may harm you and from the eye of a jealous one. Allah would cure you and I invoke the name of Allah for you."  

أَنَّ جِبْرِيلَ أَتَى النَّبِيَّ ﷺ فَقَالَ يَا مُحَمَّدُ اشْتَكَيْتَ فَقَالَ نَعَمْ قَالَ بِاسْمِ اللَّهِ أَرْقِيكَ مِنْ كُلِّ شَىْءٍ يُؤْذِيكَ مِنْ شَرِّ كُلِّ نَفْسٍ أَوْ عَيْنِ حَاسِدٍ اللَّهُ يَشْفِيكَ بِاسْمِ اللَّهِ أَرْقِيكَ  

The influence of an evil eye is a fact.  

عَنْ رَسُولِ اللَّهِ ﷺ فَذَكَرَ أَحَادِيثَ مِنْهَا وَقَالَ رَسُولُ اللَّهِ ﷺ الْعَيْنُ حَقٌّ  

The influence of an evil eye is a fact; if anything would precede the destiny it would be the influence of an evil eye, and when you are asked to take bath (as a cure) from the influence of an evil eye, you should take bath.  

عَنِ النَّبِيِّ ﷺ قَالَ الْعَيْنُ حَقٌّ وَلَوْ كَانَ شَىْءٌ سَابَقَ الْقَدَرَ سَبَقَتْهُ الْعَيْنُ وَإِذَا اسْتُغْسِلْتُمْ فَاغْسِلُوا