The Shaykh mentioned some of the verses that were difficult for some of the Companions.

The Shaykh : Some may find it strange when I say that no one can be independent or self-sufficient in understanding the Qur'an, even if he were the most eloquent, the most understanding, the most articulate, and the most expressive of the Arabs. And who is more eloquent and more understanding of the Arabic language than the Companions of the Prophet (peace and blessings be upon him), to whom the Qur'an was revealed in their language? Yet some verses were difficult for them; they did not understand them, so they turned to the Prophet (peace and blessings be upon him) and asked him about them. Among these is what the Imam al-Bukhari narrated in his Sahih and the Imam Ahmad in his Musnad from 'Abdullah ibn Mas'ud (may Allah be pleased with him) that when the Prophet (peace and blessings be upon him) recited to his Companions the saying of Allah, Blessed and Exalted is He: This verse was difficult for the Companions of the Prophet (peace and blessings be upon him), just as other verses were difficult for them. Not because they did not understand it like this one, but because of the ruling in it which contains some severity. I am not now in the position of discussing that, but rather I am in the position of explaining what was difficult for them from this noble verse: They said, "O Messenger of Allah, which of us has not committed injustice? Which of us has not committed injustice?" By this, they meant that they understood the injustice in this noble verse to mean any injustice, whether it be the injustice of a servant to himself, or the injustice of a servant to his companion, or to his family, or the like. So the Messenger (peace be upon him) clarified to them that the matter is not as it first occurred to their minds, and that the injustice here is only the greatest injustice, which is associating partners with Allah, Mighty and Majestic. And He reminded them of the saying of the righteous servant Luqman when he said to his son: And if the Companions of the Prophet (peace and blessings be upon him), who were the pure Arabs, found this wording from this noble verse difficult, and the difficulty did not remain with them except by the clarification of the Prophet (peace and blessings be upon him), this is what Allah, Mighty and Majestic, indicated in the previous verse: And therefore.