Tafsir of Ya seen 36:61

(And that you should worship Me) is a conjunction to (that you should not worship Satan), on the basis that (that) is explanatory of the covenant which contains the meaning of speech without its letters, or it is a verbal particle (masdariyyah) from which the preposition has been omitted. That is: "Did I not covenant with you to abandon the worship of Satan and to worship Me?" The prohibition was placed before the command because the right of clearing (takhliyah) takes precedence over adorning (tahliyah).

It is said: It is connected to His, the Exalted’s, saying: (This is a straight path) based on the view that the reference is to His—the Exalted’s—worship, as that is what is known as the straight path. Some have made the reference to that which was covenanted to them: the abandonment of the worship of Satan and the performance of the worship of Allah, the Majestic and Exalted. This is favored by the fact that His worship—the Exalted—if it is not separated from the worship of other than Him, the Glorified, is not termed a "straight path." So contemplate this.

The sentence is a resumption (isti'nafiyyah) brought to clarify the requirement for the covenant of His worship—the Exalted—or for both parts of the covenant. The indefiniteness (tankir) is for exaggeration and glorification, meaning: "This is a path extreme in its straightness, encompassing everything that it ought to be, and an origin for a rank that description and definition fall short of." Hence, it was not said, "This is the straight path," even though that would have implied restriction.

It is also permitted that the indefiniteness is for partiality (tab'id), meaning: "This is a portion of the straight paths," which is a minimizing of its right in the view of fair-minded discourse. It includes a subtle rebuke, in the sense that if it were merely a part of the paths described as straight, that would suffice for one to follow it; how much more so when it is the very origin and the foundation? As it is said: "I say 'some people' about you as an allusion for fear of the slanderers, while you are all of mankind." Within this is the point that what is required is straightness, and the matter revolves around it, and a little of it is much.