Commentary
The argumentation referred to in verse 65 was to decide whether Sayyidna Ibrahim (علیہ السلام) followed the way of the Jews, or that of the Christians. The futility of their exercise already stood exposed as both these ways in religion appeared long after the revelation of the Old and New Testaments. These just did not exist before that. How, then, could it be claimed that Sayyidna Ibrahim (علیہ السلام) . It adhered To these ways?
Verse 66 points out to the hollowness of their approach when they indulged in their argumentation on the basis of incomplete knowledge. That they would venture to do so on the basis of no knowledge could hardly he explained. The truth is that only Allah knows the way of Ibrahim (علیہ السلام) .
That way has been described in Verse 67.
Verse 68 declares that the closest of people to Sayyidna Ibrahim (علیہ السلام) were those who followed him during his time and now the closest to him is the Prophet of Islam, Muhammad a1-Mustafa ﷺ and so are the believers in him and in past prophets. These believers are the community of Muhammad ﷺ and their guardian is Allah and He will reward them for their belief.