What is the meaning of 'the first three generations', which the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, described as the best? Are they the first three hundred years or something else? When do these generations end?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

It is narrated on the authority of ‘Imraan ibn Husayn that the Messenger of Allaah, sallallaahu ‘alayhi wa sallam, said: “The best of generations is my generation, then the following generation, and the generation that follows." ‘Imraan said: "I do not know whether the Prophet, sallallaahu ‘alayhi wa sallam, mentioned two or three generations after his generation.” [Al-Bukhari and Muslim]

Scholars held different opinions regarding the meaning of the word “generation” in the Hadeeth, which Imaam An-Nawawi mentioned in his commentary on Saheeh Muslim saying: “Scholars held different opinions regarding the meaning of the word 'generation' in this Hadeeth. Al-Mugheerah said: 'The generation of the Prophet, sallallaahu ‘alayhi wa sallam, means his Companions and 'the following generation' means their children and the third (generation) is the grandchildren of the Companions.'

Shahr said: 'His generation refers to those who saw him, the second refers to those who saw those who saw the Prophet, sallallaahu ‘alayhi wa sallam, and so on. Some others said that it refers to a group of people who exist in the same period of time. It was also said that it refers to the people of a specific period of time in which a prophet was sent, no matter how long or short it is.' Al-Halabi mentioned that the difference is concerning the number of years varying from ten to one hundred and twenty years until he said: 'The sound opinion is that the generation of the Prophet, sallallaahu ‘alayhi wa sallam, refers to his Companions, the second refers to the Taabi‘oon while the third refers to the followers of the Taabi‘oon.'"

By this, it becomes clear to the questioner what is meant by “generations”, and the preponderant opinion concerning this matter.

Allaah Knows best.