Is it permissible for someone who enters the mosque on Friday and finds it full to sit down immediately due to being unable to perform the Salutation of the Mosque, or should he remain standing until the prayer is established?

"Tahiyyat al-Masjid" (Greeting of the Mosque) is a confirmed Sunnah for someone who enters the mosque in a state of purity (wudu') and intends to sit, based on the Prophet's (peace and blessings be upon him) saying: "When any of you enters the mosque, let him pray two rak'ahs before he sits." Exceptions to this include times of prohibition (after Fajr until the sun rises and is high, at midday, and after Asr until sunset), where the Shafi'is hold the view that it is permissible to pray it because it has a specific reason, and this is the stronger opinion. Its prayer is also prescribed even if the Imam is delivering the Friday sermon. The Greeting of the Mosque can be fulfilled by any obligatory or supererogatory prayer, because the intention is to occupy the place with prayer. The greeting is not forfeited by sitting; rather, it is permissible to stand up and pray it even if a long time has passed. Accordingly, it is permissible to sit if performing the greeting is difficult, and it should be prayed before the establishment of the Friday prayer if possible; otherwise, there is no sin upon the worshipper.