Comentario sobre Josué 1:1

And after the death of Moshe. This is connected to the chapter of the Torah¹The spirit of prophecy did not rest upon Yehoshua until the thirty day mourning period for Moshe was over. It was then that God began to speak to him and command him to begin the conquest of Eretz Yisroel. Yehoshua was in a state of sadness and the spirit of propecy does not rest upon a person who is sad. There are other Seforim in Tanach such as Ruth, Esther, Yonah that begin with the word וַיְהִי, and it was, that are not connected to any previous event. But here the beginning is definitely connected with the conclusion of Sefer Devorim where the death of Moshe is related. which concluded with the passing of Moshe;²Devorim 34:5,6,7,8. and this (Seifer Yehoshua) is connected to it.³Devorim 34:9.

The Vov comes to explain and add and to join to why the Torah finishes with the death of Moshe, and it says that after this Hashem said to Yehoshua etc.

...Behold, Yehoshua son of Nun is referred to as the assistant of Moshe, to show that the reason that he merited prophecy was because he was Moshe's assistant. This is because through being Moshe's assistant, he was constantly with Moshe, to learn from his wisdom and behaviour. This is knowledge that a student who does not remain in the vicinity of their teacher to assist them does not acquire. This is why it says "The mouth of Elisha son of Shafat, who poured water through Eliyahu", this refers to what he taught, as serving and assisting a great person is more worthwhile than learning from them, as our Sages taught.