In Parashat Bereshit, Rashi comments 3 times the words Nefesh Chaya נפש חיה (Bereshit 1:20 ; 1:21 and 1:24) the same way which is: "נפש חיה: שיש בה חיות", translated by www.chabad.org "living creatures: That there should be life in them". Why is Rashi repeating the same thing 2 other times? What do we learn from these repetitions? Any help to understand Rashi's comment would be appreciated.
The Gur Aryeh (Genesis 1:20) explains that Rashi's intent is that נפש חיה doesn't mean 'the nefesh of a haya', but rather 'a nefesh that is haya'. That is, 'haya' is an adjective; not a noun. would one read it as a noun (which would be an easy mistake to make, given that the word חיה is frequently a noun, not a verb), it would mean that hayot are the subject of the verse. This is incorrect, as the Gur Aryeh notes, since the subject is fish; not hayot. Therefore, Rashi clarifies that 'haya' is an adjective, not the subject of the sentence.
Regarding the repetition, the Gur Aryeh explains that Rashi decided to repeat the comment, since although one would realise that in the first verse 'haya' is a not a noun, one would not necessarily realise this in the next verse. In the first verse, the term 'nefesh haya' is used to refer to what has already been describes as 'sherets'. However, the next verse does not describe it as 'sherets', and therefore one might have thought that the subject of the verse is a 'haya'. Therefore, he again has to clarify the 'haya' is not a noun. The reason that 'sherets' differs from 'haya' seems to be that it connotes an animal that is close to the ground as Rashi explains in verse 20. A typical 'haya' is larger, and therefore one would be more likely to make the mistake that 'haya' is a noun, and the subject in verse 20.
Furthermore Rashi has to repeat himself a third time, since the mistake would be easiest to make in verse 24. There the verse actually deals with land animals as opposed to fish, so reading 'haya' as a noun, would be an even easier mistake.