Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear brother in Islam, we do really appreciate your question, which reflects your keenness to get yourself well-acquainted with the teachings of Islam in addition to your apparent care about seeking halal means of living. May Allah bless your efforts in pursuit of knowledge and keep you firm in the straight Path!
Regarding the content of Friday khutbah, Sheikh Sayyed Sabiq, states in his well-known book Fiqh As-Sunnah:
It is preferred that the Friday khutbah includes 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 Friday Prayer 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…” [Surat 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.”
Allah Almighty knows best.