Ma'arif al-Qur'an
Mufti Muhammad Shafiوَالْبَحْرِ الْمَسْجُورِ (and by the sea, filled up with fire...52:6) The word bar means sea and the passive participle masjur is derived from sajr which is used in several different senses, one of which is to kindle with fire. Some of the commentators interpret the participle in this sense here, that is, by the sea which will be kindled with fire on the Day of Resurrection, just as Allah said in another verse وَإِذَا الْبِحَارُ سُجِّرَتْ "And when the seas will be kindled with fire". In other words, it will be kindled with fire and become a raging fire surrounding the people in the plain of hashr. This was reported by Sayyidna Said Ibn Musayyab from Sayyidna Ali Ibn Abi Talib ؓ . Sayyidna Ibn ` Abbas, Mujahid, and ` Ubaidullah Ibn ` Umair ؓ also report likewise. (Ibn Kathir)A Jewish person asked Sayyidna ` Ali ؓ 'where is the Hell?'. He replied 'the sea'. The Jew, who was the scholar of the previous scriptures, confirmed this. (Qurtubi) Sayyidna Qatadah ؓ and others interpreted the phrase to mean 'filled sea'. Ibn Jarir (رح) preferred this interpretation (Ibn Kathir).
' This is the interpretation adopted by Maulana Ashraf Thanawi (رح)