Charles Ellicott Commentary Numbers 27:18

"And Jehovah said unto Moses, Take thee Joshua the son of Nun, a man in whom is the Spirit, and lay thy hand upon him;" — Numbers 27:18 (ASV)

In whom is the spirit ... — The definite article is not used in the original. The word translated “spirit” appears to denote spiritual endowment and qualifications.

And lay your hand upon him— It should be noted that the spiritual qualifications of Joshua did not supersede the necessity of an outward consecration to his office. Moreover, it seems that special qualifications for the office were bestowed in connection with the imposition of the hands of Moses, for it is written in Deuteronomy 34:9 that Joshua the son of Nun was full of the spirit of wisdom; for Moses had laid his hands upon him.