The concept of the descent of Jesus (PBUH) is included in the category of beliefs. Just like the beliefs in monotheism, prophethood, and the afterlife, the descent of Jesus (PBUH) is considered a belief that must be held. The intention is that Muslims should believe that Jesus will descend from heaven and kill the Dajjal. This is one of the signs of the Day of Judgment, to occur in the future. Since this concept is based on Sahih and mutawatir hadiths, believing in it is a requirement of faith, and its denial is equivalent to disbelief.
In Aqeedat al-Tahawiyyah, a book representing the beliefs of the Hanafi legal school, it is written:
ونؤمن بأشراط الساعة منها: خروج الدجال ونزول عيسى ابن مريم عليه السلام من السماء.
We believe in the signs of the Hour, including the emergence of the Dajjal and the descent of Jesus, son of Mary, from heaven. (1/59)
In Al-Fiqh Al-Akbar, attributed to Imam Abu Hanifa, it is stated:
خروج الدجال ويأجوج ومآجوج وطلوع الشمس من مغربها ونزول عيسى عليه السلام من السماء وسائر علامات يوم القيامة على ما وردت به الأخبار الصحيحة حق كائن.
The emergence of the Dajjal, and Gog and Magog, the sun rising from the west, the descent of Jesus from heaven, and all other signs of the Day of Judgment mentioned in the authentic reports are true and will occur. (72)
Imam Nawawi in his commentary on Sahih Muslim writes:
قال قاضي رحمه اللّٰه: نزول عيسى عليه السلام وقتله الدجال حق وصحيح عند أهلِ السنة، للأحاديث الصحيحة في ذلك. وليس فى العقل ولا فى الشرع ما يبطله فوجب إثباته.
Qadi Iyad (may Allah have mercy on him) said: The descent of Jesus and his killing of the Dajjal at his hand are true and correct according to Ahl al-Sunnah, due to the authentic hadiths on these matters. There is nothing in reason or Shariah that invalidates these beliefs, so its affirmation is obligatory. (Sharh al-Nawawi 'ala Muslim 7/599)
Imam Jalaluddin Suyuti, while arguing for the status of Jesus (PBUH) and refuting a counterclaim tells his interlocutor that the latter’s claims entails:
إما نفي نزول عيسى، أو نفي النبوة عنه وكلاهما كفر؟
Denying either the descent of Jesus (PBUH) or his prophethood constitutes disbelief (kufr). (Al-Hawi lil-Fatawi 2/201)