Is a sermon necessary for a lunar eclipse, and should it be lengthy?

A sermon after the eclipse prayer is sunnah (recommended), and this is the madhhab (school of thought) of Imam Shafi'i, one of the two opinions of Imam Ahmad, and the view of the majority of the Salaf. The Prophet (peace be upon him) delivered a sermon after the eclipse prayer, praising and extolling Allah, then admonishing the people. Some scholars believe that the sermon consists of two parts, with a sitting in between, while others hold that it is a single sermon. Abu Hanifa and Ahmad, in his well-known opinion, differed on this, believing that the Prophet (peace be upon him) delivered the sermon to clarify rulings. As for the Malikis, they view admonition as recommended, but not a formal sermon. The Sunnah is to shorten the sermon to achieve the objective without causing boredom.