Is the Friday sermon considered a substitute for the two rak'ahs of Dhuhr, and what is the ruling and the opinions regarding that?

The correct view is that the khutbah (sermon) is not a substitute for the two rak'ahs of Dhuhr (noon prayer). The evidence for this is the hadith of Jabir ibn Abdullah, narrated by Muslim and Ibn Khuzaymah, where the Prophet, peace and blessings be upon him, ordered Sulayk al-Ghatafani to stand and perform two light rak'ahs while the Imam was delivering the khutbah. If the khutbah were a substitute for the two rak'ahs, it would suffice for anyone entering the mosque, making the tahiyyat al-masjid (greeting of the mosque prayer) unnecessary.

Imam al-Iraqi, in Tarh al-Tathrib, presented arguments confirming that the khutbah is not a prayer: 1. If a worshiper enters while the Imam is already praying, that suffices as a greeting to the mosque, because the purpose is to occupy the space with prayer. 2. The Prophet, peace and blessings be upon him, distinguished between prayer and the khutbah, saying: "If the prayer is established, then there is no prayer except the obligatory one." Yet, he ordered the one who entered to perform the greeting prayer while the Imam was delivering the khutbah. 3. What is forbidden in prayer, such as speech and actions, is not forbidden during the khutbah. It is established that the Prophet, peace and blessings be upon him, interrupted his khutbah to teach the Bedouin. Similarly, it is permissible for the khatib (preacher) to descend, walk, drink, and eat a small amount, which is not permissible in prayer.

Moreover, many scholars permit the khutbah to be muhdatha (newly innovated or subject to change), which is not the case for prayer by consensus. Imam Ahmad permitted a person in a state of janabah (major ritual impurity) to deliver the khutbah, then perform ghusl (ritual bath) and pray, which is not permissible for prayer. Prayer requires facing the Qiblah, while the khutbah requires facing away from it (i.e., facing the congregation). The Hanbalis held the view that the two khutbahs are a substitute for the two rak'ahs.