Is the Hadith that speaks of saying "Amin" upon entering the mosque and that the angels pray for the one who says it, and which was narrated by Abu Hurayrah, authentic?

It has been authentically reported from the Prophet, peace and blessings be upon him, specific supplications for entering the mosque, among them: "O Allah, open for me the doors of Your mercy," and "I seek refuge in Allah, the Almighty, in His Noble Countenance, and His Eternal Sovereignty, from Satan, the accursed."

As for saying "Amin" upon entering the mosque, it has not been reported from the Prophet, peace and blessings be upon him, nor from his companions, nor has any scholar held this view. Rather, it is closer to innovation (bid'ah); because the Hadith that might be relied upon (the angels' supplication for the worshipper) does not indicate saying Amin upon entering the mosque, but rather upon sitting in one's place of prayer.

One must adhere to what the Prophet, peace and blessings be upon him, legislated, without addition or subtraction. For the silence of the Sacred Law on a matter despite the presence of its cause indicates that any addition to it is an innovation.