The meaning of "la" in the phrase "fa la aqsim"

The Shaykh : And I ask first about the "la" in His saying: Is it a negation or for emphasis? Some exegetes say it is a negation, and then they differed regarding what is negated. It was said that "la aqsim" means that the matter does not require an oath, for it is clearer and more evident than needing to swear an oath about it. On this view, it negates the oath in the sense that the oath is not needed here because of the clarity of the matter about which the oath is made. It was also said that it is a negation and the negated part is omitted, with the implied meaning being "there is no truth or acceptance" for what these people have denied of this Noble Qur'an. Some exegetes held that the "la" here is not a negation but is for emphasis, because what follows is a matter of great importance that requires attention and awareness. This is the correct view, and the "la" is intended to alert the addressee, meaning "pay attention to what will be conveyed to you." Then he resumed and said, "I swear by the positions of the stars, and it is indeed an oath," and so on.