He should give it a warning three times. If it appears to him after that, he should kill it, for it is a devil.
فَلْيُؤْذِنْهُ ثَلاَثًا فَإِنْ بَدَا لَهُ بَعْدُ فَلْيَقْتُلْهُ فَإِنَّهُ شَيْطَانٌ
There is a group of jinns in Medina who accepted Islam, so he who would see anything from these occupants should warn him three times; and if he appears after that, he should kill him for he is a satan.
قَالَ رَسُولُ اللَّهِ ﷺ إِنَّ بِالْمَدِينَةِ نَفَرًا مِنَ الْجِنِّ قَدْ أَسْلَمُوا فَمَنْ رَأَى شَيْئًا مِنْ هَذِهِ الْعَوَامِرِ فَلْيُؤْذِنْهُ ثَلاَثًا فَإِنْ بَدَا لَهُ بَعْدُ فَلْيَقْتُلْهُ فَإِنَّهُ شَيْطَانٌ
There is a group of jinns in Medina who accepted Islam, so he who would see anything from these occupants should warn him three times; and if he appears after that, he should kill him for he is a satan. (Using translation from Muslim 2236c)
قَالَ رَسُولُ اللهِ ﷺ «إِنَّ بِالْمَدِينَةِ نَفَرًا مِنَ الْجِنِّ أَسْلَمُوا فَمَنْ رَأَى شَيْئًا مِنْ هَذِهِ الْعَوَامِرِ فَلْيُؤْذِنْهُ ثَلَاثًا فَإِنْ بَدَا لَهُ بَعْدُ فَلْيَقْتُلْهُ فَإِنَّهُ شَيْطَانٌ»