Allah Ta’ala berfirman:

وَأَنْكِحُوا الْأَيَامَى مِنْكُمْ وَالصَّالِحِينَ مِنْ عِبَادِكُمْ وَإِمَائِكُمْ إِنْ يَكُونُوا فُقَرَاءَ يُغْنِهِمُ اللَّهُ مِنْ فَضْلِهِ وَاللَّهُ وَاسِعٌ عَلِيمٌ

"And marriage is the people who like you, and those who are worthy (mating) of your male servants who are male and your servants who are women. If they are poor God will enable them with His grace. And Allah is knowledgeable (His gift) is the Knower "(Surat an Nur: 32).

In this verse there is an order to get married. Even the ulama disagree to marry which is mandatory or is the sunnah to be 3 members:

First opinion

The School of Dhahiri believes that the law of marriage is mandatory, and the unmarried person is sinful. They postulate with the above verse, which uses the command sentence وَأَنْكِحُوا (and marry it ...) and the order shows the mandatory law.

They also said that getting married is a way to keep yourself from being haram. And the rule says:

ما لا يتم الواجب إلا به فهو واجب

"Imperfect obligations except with something, then something is mandatory"

Second opinion

Syafi'i School of thought argues that the law of marriage is mubah, and the unmarried person is not sinful. Imam Asy Syafi'i said that marriage is a means of channeling lust and achieving the pleasure of lust (the lawful), then the law is changed just like eating and drinking.

Third opinion

The opinion of the ulum jumhur, namely the Maliki school, Hanafi and Hambali argues that the marriage law is mustahab (sunnah) and not until mandatory.

They postulate with the following points:

1. Suppose marriage is mandatory, of course the history of the Prophet sallallaahu'alaihi Wasallam stated that because marriage is a necessity that is needed by everyone. Whereas we meet among friends of the Prophet who are not married. Likewise, we have met people since the time of the Prophet sallallaahu'alaihi Wasallam until our time, there are some who are not married at all. And it is not surprising that even one of his denials on this matter.
2. If marriage is mandatory, then a guardian may force his daughter to marry. Though forcing girls to marry is actually prohibited by the Shari'a. Based on the words of the Prophet Shallallahu'alaihi Wasallam:

ولا تُنْكَح الثيب حتى تستأمر

read more here : https://muslim.or.id/25059-apakah-menikah-itu-wajib.html