Hadith: A solar eclipse occurred during the Prophet's lifetime and he sent someone to summon people for a congregational prayer. They gathered and he came forward and began the prayer by making Takbīr. He bowed four times and prostrated four times in two Rak‘ahs

عن عائشة رضي الله عنها «أن الشمس خَسَفَتْ على عهد رسول الله صلى الله عليه وسلم فبعث مُناديا ينادي: الصلاة جامعة، فاجْتَمَعوا، وتقَدَّم، فكَبَّر وصلَّى أربعَ ركعات في ركعتين، وأربعَ سجَدَات».
[صحيح] - [متفق عليه]

‘Ā'ishah (may Allah be pleased with her) reported that A solar eclipse occurred during the Prophet's lifetime and he sent someone to summon people for a congregational prayer. They gathered and he came forward and began the prayer by making Takbīr. He bowed four times and prostrated four times in two Rak‘ahs.
[Authentic hadith] - [Narrated by Bukhari & Muslim]

Explanation

An eclipse of the sun occurred during the lifetime of the Messenger of Allah (may Allah's peace and blessings be upon him), so he sent a caller through the streets and markets to call people to pray and invoke Allah, Blessed and Exalted, to forgive them, have mercy on them, and maintain His apparent and hidden blessings upon them. They gathered in his mosque, and he stepped forward to his place where he leads them in prayer. He led them in a prayer that was different from that they were accustomed to due to the occurrence of an extraordinary universal sign. There was no Iqāmah. He began the prayer by saying Takbīr and performed two Rak‘ahs each containing two bows and two prostrations.