Al-wasīlah: anything by which one draws near to Allah. Thus, seeking a wasīlah to Allah means performing a deed that brings a person closer to Him.

“and they hope for His mercy”: that is, they place their hope in none but Him.

“and they fear His punishment”: that is, they fear no one but Him.

Overall meaning of the verse: Allah states that those beings whom the polytheists invoke instead of Him—whether angels, prophets, or the righteous—hasten to seek closeness to Allah; they hope for His mercy and fear His punishment. Since this is their state, they are nothing but servants. How, then, can they be called upon alongside Allah while they themselves are occupied with their own concerns, supplicating to Allah and seeking nearness to Him through acts of worship?

Relevance of the verse to the chapter: It shows that the essence of tawḥīd and of bearing witness that there is no deity but Allah is to abandon the practice of the polytheists who call upon the righteous and seek their intercession with Allah to remove or avert harm, for such behavior constitutes major shirk.

Points derived from the verse:
1- A rebuttal of those who appeal to saints and the righteous for relief from hardship or for the attainment of benefit, for these invoked beings do not possess the power to avert harm or bring benefit even for themselves—so how could they do so for others?
2- It highlights the profound fear that prophets and the righteous have of Allah and their ardent hope for His mercy.