وَلَسَوْفَ يُعْطِيكَ رَبُّكَ فَتَرْضَىٰ
سَوْفَ (sawfa) is the particle of the future. Arabic has two instruments for stating the future: سَ (sa-), attached to the front of the verb, and سَوْفَ, which comes as a separate word. The general opinion of the lexicographers is that sawfa states a wider and more distant future. That is, not "presently" but "in time to come".
The lām and sawfa coming together is rare in Arabic. Their combination means this: certainly, but the time is not now.
In point of context this is an entirely honest expression. The addressee's expectation was "now"; that is exactly why the silence weighed. The verse does not pull the expectation into the present — it says "in time to come". But by setting an emphasis before that "in time to come", it separates the delay from uncertainty.
Root: ع-ط-و/ي, in Form IV aʿṭā: to give. The properties of this verb were treated in the section on Sūrat al-Kawthar (innā aʿṭaynāka'l-kawthar). In brief: some of the lexicographers draw a distinction between aʿṭā and ītāʾ and characterise aʿṭā as a giving of the kind that is a gift, without return. The distinction is not absolute, but it is recorded.
Yuʿṭīka — "He will give to you". Give what? The sentence has no object. This performs the reverse function of the omission in the third verse: there the dropping of the object protected (it kept the verb of loathing away from the addressee); here the dropping of the object opens out. What is not named cannot be bounded.
In a promise, the amount not being stated can mean one of two things: either what will be given is small and it is not wished to be said, or it is so wide that no one name can close it off. The next sentence determines which.
Root: ر-ض-و/ي. To be content, to be well pleased, to accept. Its derivatives: riḍā, marḍāt (good pleasure), rāḍī (the one who is content), marḍī/marḍiyya (the one with whom one is content).
The real matter is the measure. The measure of a promise is normally the object: "I will give this much", "I will give this". An amount or a kind is stated, and the addressee weighs it accordingly.
Here the measure is not the object but the state of the subject. How much will be given is not said; what is said is as much as will content you.
In practice this difference is large. A word given in terms of an amount leaves open the question whether the amount will be enough. A person may receive a great deal and still not be content — this is something observed, the rule rather than the exception. The verse closes this gap: the promise is tied not to the amount of what is given but to the satisfaction of the one who receives.
In the Qurʾān riḍā is rarely one-sided. In the places where the word occurs most densely it works both ways:
The last example matters particularly, because it is one of the sūras of the same period and it describes riḍā as a point of arrival. Al-Ḍuḥā 5 promises that point of arrival to one person.
Various explanations of the content of this promise are given in the classical works of tafsīr: his station in the hereafter, al-Kawthar, intercession, the forgiveness of his community, the establishment of the religion upon the earth.
In one report it is transmitted that the Prophet said he would not be content as long as even one person of his community remained in the Fire. This report is frequently cited in the books of tafsīr in connection with this verse, but its soundness is disputed and it is not found with this wording in the sound collections of ḥadīth. Its being transmitted in the language of certainty must be approached with caution.
The text itself does not state the content. And its not stating it follows from what was said above: what is named is bounded.