What is the ruling on those who joke or threaten brothers with the evil eye?
Ash-Shaykh Saalih al-Fawzaan, may Allah preserve him, said when he was asked regarding a person who threatens his coworkers with the evil eye,
: اشتكوه إلى المسئول يبعده عنكم، أو يفصله لأن هذا مؤذي، يفصله من الوظيفة أو ينقله إلى ناس يطبعونه ويمسكونه الجادة.
Make a complaint about him to the one who is responsible for him. (This is in order) to keep him far from you or to remove him from the work site. Since he is harmful, he should be removed from the job, or they should move him to a people who he will become normal and serious with.
A Side Note: Those who joke or threaten others with the evil eye have fell into a sin due to the hadeeth:
عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِي لَيْلَى، قَالَ حَدَّثَنَا أَصْحَابُ، مُحَمَّدٍ صلى الله عليه وسلم أَنَّهُمْ كَانُوا يَسِيرُونَ مَعَ النَّبِيِّ صلى الله عليه وسلم فَنَامَ رَجُلٌ مِنْهُمْ فَانْطَلَقَ بَعْضُهُمْ إِلَى حَبْلٍ مَعَهُ فَأَخَذَهُ فَفَزِعَ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم “ لاَ يَحِلُّ لِمُسْلِمٍ أَنْ يُرَوِّعَ مُسْلِمًا”
Narrated AbdurRahman ibn AbuLayla:
The Companions of the Prophet (ﷺ) told us that they were travelling with the Prophet (ﷺ). A man of them slept, and one of them went to the rope which he had with him. He took it, by which he was frightened. The Prophet (ﷺ) said: It is not lawful for a Muslim that he frightens a Muslim.
Source: Sunan Abu Dawud 5004