This research deals with the grammatical aspects that prepositions and their genitives can bear, as Imam Al-Qastalani discussed in his book Irshad Al-Sari, in which he explained Sahih Al-Bukhari. Imam Al-Qastalani appears in this book as a grammarian who is familiar with the opinions of grammarians and a narrator who is familiar with the various narrations. The research initially addressed the definition of Imam Al-Qastalani and his book Irshad Al-Sari. Then the research addressed the applied aspect by analyzing examples of the noble prophetic hadith in which the letters of Har and their genitives were mentioned, which can bear more than one grammatical aspect. We explained these aspects in them, and the meanings of the letters of Har. We also mentioned the different narrations of the hadith, if any, that are related to the issue under study, and we mentioned the opinions of grammarians and some interpreters of the noble prophetic hadith on the issue under study. The difference between grammarians had a prominent effect on the difference between interpreters of the noble prophetic hadith, especially grammarians who permitted the use of the noble prophetic hadith in grammatical issues, and took the words of the Prophet, may God bless him and grant him peace, as evidence for constructing the grammatical rule and explaining the meanings of prepositions, the subject of the study. It became clear from During the study, the validity of the authenticity of the noble prophetic hadith was confirmed by its agreement with the grammatical rules derived primarily from the Holy Qur’an and the speech of the Arabs. Therefore, the speech of the master of eloquent Arabs was a strong argument for the grammatical rules, supporting them and giving their meanings. Among these meanings are the meanings of prepositions with their object and what they bear in terms of grammatical aspects.