What is the meaning of the phrase "and Allah decrees through the tongue of His Prophet whatever He wills" in the Hadith: "Intercede and you will be rewarded, and Allah decrees through the tongue of His Prophet whatever He wills"?

This Hadith was narrated by Bukhari, Muslim, and others, on the authority of Abu Musa Al-Ash'ari, may Allah be pleased with him. The meaning of his (peace and blessings of Allah be upon him) saying: "And Allah decrees through the tongue of His Prophet what He wills," is that the fulfillment or non-fulfillment of a petitioner's need is by the will and decree of Allah. And that the intercessor is rewarded for his intercession in all cases, whether his intercession is accepted or not. And that whatever judgment is issued by the Messenger (peace and blessings of Allah be upon him) regarding the petitioner's matter is by the decree of Allah the Almighty, whether his need is fulfilled or not.