My question is about entering the mosque with bodily or clothing impurity (najāsa)?

The fundamental principle is that a Muslim should guard against impurities and promptly wash away anything that touches them. Mosques must also be kept free from impurities, as indicated by the Almighty's saying: (In houses which Allah has permitted to be raised, and His name to be mentioned therein). Ibn Kathir, in his exegesis, said regarding this verse: "meaning, Allah commanded that they be maintained and purified from defilement." For this reason, jurists prohibited menstruating women from passing through the mosque for fear of defiling it. The Malikis also prohibited teaching a child in the mosque because of their inability to guard against impurities. Some Shafi’is forbade entering the mosque with impurity on one’s garment or shoe, whether wet or dry, if there was a fear of defiling the mosque or if the entry was not for a necessity. Accordingly, it is forbidden to enter and remain in the mosque for anyone who has an impurity on their body or clothing until they remove it. Similarly, it is forbidden to pass through it without necessity or if there is a fear of defiling it.