Commentary for Numbers 27:22

ויקח את יהושע AND HE TOOK JOSHUA — he took him by fine words and told him the reward that will be given to Israel’s leaders in the world to come (Sifrei Bamidbar 141:2).

ויעש משה כאשר צוה ה׳ אותו, Moses did as G'd had instructed him, etc. The reason the Torah mentions something so obvious as Moses complying with G'd's instructions, is only to tell us that he did so promptly after having been so instructed. It also means that had Moses not specifically requested that G'd appoint a suitable leader now, G'd would not yet have given such instructions. Seeing that Moses' death was not that near at hand, and that there was no immediate need to appoint Joshua, Moses' conduct was a credit to him.

He persuaded him verbally. Rashi is answering the question: It is already written, “Moshe did as Hashem commanded him,” so why is it necessary to say, “He took Yehoshua”? Rashi answers that “He persuaded him…” meaning that he said more to him than Hashem had said. For Hashem only commanded him to say, “You are fortunate that you have merited this…” However Moshe informed him “of the reward…” The reason was so that he would not say, “Of what benefit is this aggravation to me?” given that Moshe and Aharon had been punished because of the people. He therefore informs him of the reward.