Is it permissible to say 'amin' to the supplication made during the Friday sermon?

Islamic scholars, taking into account both the hadiths regarding Friday and the practice of the Messenger of Allah (s.a.s.), have determined the essential pillars of the sermon, the conditions to be observed in a valid sermon, and its etiquettes. (Kâsânî, Bedâ’i, 1/263) There are hadiths stating that it is not appropriate for the congregation to speak while the preacher is delivering the sermon. (Bukhari, Jumu‘a, 36 [934]; Muslim, Jumu‘a, 11 [851]; Muwatta’, Jumu‘a, 6; Abu Dawud, Salat, 234 [1112]; Tirmidhi, Jumu‘a, 368 [512]; Nasa’i, Jumu‘a, 22 [1401]) Based on these hadiths, the Hanafis and Shafi‘is consider speaking during the sermon as disliked (makruh), while the Hanbalis and Malikis regard it as forbidden (haram). (Kâsânî, Bedâ’i, 1/263; Shirbini, Mughni’l-muhtaj, 1/553) On the other hand, Islamic scholars, again considering the practice of the Messenger of Allah (s.a.s.), have stated that supplicating for the believers during the sermon is recommended (mandub) or an essential pillar (rukn). (Kâsânî, Bedâ’i, 1/263)

Accordingly, the sermon should be listened to attentively, and one should not engage in other activities or speak during it. However, quietly reciting salawat when the Prophet’s (s.a.s.) name is mentioned and saying ‘amin’ to the preacher’s supplication are not considered as speaking, so there is no harm in doing these. (see Kâsânî, Bedâ’i, 1/264; Ibn Abidin, Radd al-Muhtar, 2/158-159)

Source: T.C. Diyanet İşleri Başkanlığı, Din İşleri Yüksek Kurulu