There is nothing in the authentic sources of Shari`ah to the effect that it is obligatory to mention the names of the four caliphs, the name of the Prophet’s uncle `Abbas, the Prophet’s daughter Fatimah, and his grandsons in the second khutbah of Friday Prayer. However, it is preferable that the Friday khutbah include praises of Allah, the Exalted, prayers upon the Prophet, admonitions, and Qur’anic recitations. Also, there is nothing wrong in sending peace and blessings on the Rightly guided Caliphs and the Prophet’s family without believing that this is obligatory or one of the pillars of the khutbah without which it would be invalid.
Sheikh Sayyed Sabiq, states in his well-known book, Fiqh As-Sunnah: “It is preferred that the Friday khutbah include praises of Allah, the Exalted, prayers upon the Prophet, admonitions, and Qur’anic recitations.
Abu Hurairah reports that the Prophet (peace and blessings be upon him) said: “Every speech that does not begin with the praises of Allah is defective.
In another version, it is stated: “The Friday khutbah that does not contain the testimony [There is no God except Allah, and Muhammad is His Messenger] is like the defective hand.”
Ibn Mas’ud reports that the Prophet would say in his opening testimony: “All praise be to Allah, we seek His aid and we seek His forgiveness and we seek refuge in Allah from the evil of our souls. Whomever Allah guides, no one will be able to mislead him. Whoever He leaves astray will have no guidance for him. And I testify that there is no God except Allah and that Muhammad is His slave and His Messenger whom He sent with the truth and as a warner before the Hour. Whoever obeys Allah and His Messenger will be guided aright, and whoever disobeys them will only harm his own self and he will not harm Allah, the Exalted, at all.”
Ibn Shihab was asked about the Prophet’s opening testimony during his khutbah on the day of Jumu’ah, and he said something similar to that except that he stated: “Whoever disobeys them has gone astray.”
Jabir ibn Samurah says: “The Messenger of Allah would deliver his khutbah standing, would sit in between the two khutbahs, would recite some verses, and would remind the people [about Allah].”
The obligatory nature of salatul Jumu’ah is also obvious from the hadith recorded by al-Bukhari and Muslim from Abu Hurairah that the Prophet said: “We are the last [of the people to come] but the first on the day of resurrection. They received their books before us and we got ours after them. This day was obligatory upon them, but they differed concerning it, and Allah guided us. The people, therefore, follow us: the Jews tomorrow and the Christians the day after tomorrow.”
Jabir also related that the Prophet (peace and blessings be upon him) would not make his admonitions on Friday too long, but give a very short khutbah. This is related by Abu Dawud.
Umm Hisham bint Harithah ibn an-Nu’man says: “I learnt [Surah] Qaf of the Glorious Qur’an from the Prophet for he recited it upon the pulpit every Friday when he addressed the people.”
Ibn Majah records from Ubayy that the Messenger of Allah recited: “Blessed is He… [Surah al-Mulk] on Friday while he was standing. In ar-Raudah an-Nadiyah, it is stated: “Thus the required khutbah, in terms of Islamic law, should be modeled after the Prophet’s khutbah exhorting people to do good and warning them against dire consequences of the evil. This is the spirit of the address which the Islamic law has instituted. As to the other contents of the khutbah, like praising Allah, saying prayers upon His Messengers or reciting a portion of the Qur’an, none of these is its main purpose, which is to admonish people… It has been customary among the Muslims [in the light of the sunnah] that if one wanted to make some sort of proclamation, he would begin with praises of Allah and prayers upon His Prophet, or something of that nature. Still, that is not the purpose of the khutbah; indeed, the purpose is that which is said after praises of Allah and prayers for the prophet. If a person delivers a khutbah and confines it to only praising Allah and saying prayers upon the Prophet, his khutbah would hardly be acceptable. Any person with common sense could understand that.
It is the admonitory aspect of the Friday khutbah which the hadith emphasizes, and if a khatib makes an admonition, he fulfills the purpose of shari’ah; if he precedes his khutbah with praises of Allah and prayers upon the Prophet and during his admonitions he uses Qur’anic verses, then he does it in a complete and satisfactory manner.”
Having stated the above, it becomes clear that there is nothing wrong in mentioning the names of the four first Caliphs or the Prophet’s family in the second or the first khutbah without believing that mentioning them in the second khutbah is one of the conditions for the validity of the Friday sermon.