Shaykh Ibn Uthaymin (rahimahullah) said:

Some people impose themselves during wedding occasions, taking the opportunity to speak at length, elaborating and prolonging their speech to the point of causing boredom. As a result, many people may end up disliking beneficial speech altogether because of such a person’s behavior.

People are of different types: some enjoy reminders even if they are long; some do not want them at all; some enjoy them if they are short but get bored if they are long; and some prefer to hear from one person but not from another — people differ.

It is well known that people attend weddings to express joy and happiness, to make the newlyweds happy, and to meet one another — and it may be that some do not see each other except on such occasions. They may have things they want to discuss with one another, so when someone gets up and gives a long speech, he ends up boring the people.

Furthermore, we know that we are not more eager to guide and advise people than the Messenger of Allah ﷺ  and his Companions. Yet, we do not know of the Prophet ﷺ or his Companions ever standing up to deliver admonitions to the people during such occasions. Rather, the Prophet ﷺ said to someone who had gotten married: “Why did you not send someone with her who could sing? For the Ansar are a people who enjoy entertainment.” This indicates that such occasions are for joy and celebration — not for preaching.

Yes, if a person sees something evil, then he is required to stand and speak out against it, advising the attendees accordingly. Or, if a well-known and respected individual is present and the people are keen to hear from him, and someone says to him, “O so-and-so, speak to us,” or asks him a question which opens the door for discussion — then that is good.

But for such gatherings to be made into preaching events without the attendees expecting or wanting that, and in a way that is not in accordance with the guidance of the righteous predecessors, then this is an issue. You already know that the Messenger ﷺ would occasionally choose specific times to advise his Companions so that they would not grow weary or bored. Yes.

Source: Liqa al-Bab al-Maftuh, printed version (11/10)

Shaykh Ahmad al-Najmi (rahimahullah) was asked the following question:

Honourable Shaykh, we see in some weddings that during the wedding night a formal program is arranged consisting of various segments, such as the recitation of the Qur’an, giving reminders, posing questions to the attendees, and awarding a prize to whoever answers.
Is doing such things in accordance with the way of the Salaf, or is this from the newly introduced matters in the religion? May Allah reward you with good.

Shaykh Ahmad al-Najmi (rahimahullah) answered:

All praise is due to Allah, and may peace and blessings be upon the Messenger of Allah, his family, and his companions.

To proceed: I do not know of the Salaf doing such a thing. However, if they did it occasionally for the sake of some benefit, and did not take it as an ongoing practice, then in my view, that would be permissible. But if it is taken as a regular tradition done in every wedding, then it may be regarded as an innovation (bid‘ah). And Allah is the one who grants success.

Source: Al-Fatawa al-Jaliyyah (2/331)

Translator’s Note:

It is from the Sunnah that the one conducting the marriage contract (nikah) begins with Khutbah al-Hajah and may deliver a brief and relevant introduction before initiating the actual proceedings of the nikah. This is in accordance with the practice of the Prophet ﷺ and the salaf after him.
As for what the two Shaykhs referred to, it is regarding the arrangement of something beyond this.