The concept can be explained as follows: [Don Yosef] ibn Yechia1 interprets the verse as meaning: You, [G‑d,] are obligated to forgive, and in order for You to be feared, it is fitting for You to possess the attribute of forgiveness. For when a servant transgresses against his master, he will humble himself before him if he knows that his master is merciful. (For the servant’s awareness that his master is merciful will lead to two responses: a) he will humble himself before him; and b) he will recognize and admit the transgression he committed. Since the servant’s approach is characterized by the quality of humility, he will recognize that he transgressed against his master. Therefore the outcome will be) that he will turn to his master and his master will be merciful to him2 (for the nature of the merciful is to express mercy. As a consequence,) he will forgive the servant’s transgression.

If, by contrast, the servant knows that his master is cruel and withholds forgiveness, (then even when the servant recognizes and acknowledges his transgression, because of his fundamental harshness and hardness of heart,) the servant will not humble himself before him. On the contrary, he will become even more rebellious. To cite a parallel: Our Sages relate (Chagigah 15a) that Rabbi Meir told Acher:3 “Repent.”

Acher replied to him: “I heard [a heavenly voice] behind the curtain, [saying]: ‘“Return, wayward sons”4 …except for Acher.’ I said: Since this person5 has been ostracized from that world,6 let him go and take pleasure from this world.” Thus he went out [and assumed] an entirely decadent lifestyle.

For this reason, You, [G‑d,] are obligated, [as it were,] to forgive. Since G‑d’s desire is that man conduct himself in an appropriate manner and his repentance is accepted as explained above [in the example of the servant and the master], therefore, it is appropriate that You, [G‑d,] possess the quality of forgiveness.

This explanation parallels the interpretation given by the Levush7 in the name of his teacher, Maharshal,8 on the phrase “forgiveness is Yours”: Forgiveness is Yours alone; there is nothing preventing You from forgiving. G‑d is not like a mortal king. For if a person transgresses against a mortal king but asks his forgiveness, even if the king desires to forgive him, there may be various obstacles and different restrictions [preventing him from doing so]. Firstly, there are the norms of the kingdom: sometimes there is an obstacle [to granting forgiveness, because doing so] could cause transgressors to increase and the ordered pattern of the country to be disturbed. At times, there are other obstacles. As a general rule, forgiveness is dependent on the officers and the counselors of the king.9 [With regard to G‑d, however, none of the above applies.] “Forgiveness is Yours”; [i.e., You may do whatever You wish;] there are no obstacles at all.

From his interpretation, it is understood that forgiveness comes from [the dimension of G‑dliness] described by the phrase:10 “He is not a man…,”11 i.e., a level above the Spiritual Cosmos.12 On this basis, “[For forgiveness is Yours,] so that You may be feared” refers to fear of G‑d’s very Essence. Thus the interpretation of the verse, “For forgiveness is Yours, so that You may be feared” is that the way to reach [the objective] “so that You may be feared” — [referring to] the fear of G‑d’s Essence — is through “Forgiveness is Yours,” [G‑d’s] abundant forgiveness. Through [G‑d’s granting man] abundant forgiveness, it is possible [for him] to attain this [essential] fear.

Summary

It is explained that when a servant knows that his master will forgive, he is motivated to humble himself and recognize his sins.

The explanation of the phrase “forgiveness is Yours” is that there are no obstacles [to G‑d’s granting forgiveness] because [forgiveness is granted by a level of G‑dliness] above the Spiritual Cosmos. The continuation of the verse “So that You may be feared” refers to the fear of G‑d’s very Essence.