Narrated Abu Musa RA, The Prophet ﷺ said:
مَثَلُ الْجَلِيسِ الصَّالِحِ وَالسَّوْءِ كَحَامِلِ الْمِسْكِ وَنَافِخِ الْكِيرِ، فَحَامِلُ الْمِسْكِ إِمَّا أَنْ يُحْذِيَكَ، وَإِمَّا أَنْ تَبْتَاعَ مِنْهُ، وَإِمَّا أَنْ تَجِدَ مِنْهُ رِيحًا طَيِّبَةً، وَنَافِخُ الْكِيرِ إِمَّا أَنْ يُحْرِقَ ثِيَابَكَ، وَإِمَّا أَنْ تَجِدَ رِيحًا خَبِيثَةً
“The example of a good pious companion and an evil one is that of a person carrying musk and another blowing a pair of bellows. The one who is carrying musk will either give you some perfume as a present, or you will buy some from him, or you will get a good smell from him, but the one who is blowing a pair of bellows will either burn your clothes or you will get a bad smell from him.”
Sahih al-Bukhari (5534)