Or HaChaim on Genesis 2:8/אור החיים על בראשית ב׳:ח׳

1 ויטע השם אלוקים. The Lord G'd planted. The reason the Torah interrupts the sequence of G'd's planting all kinds of trees in that garden (verses 8 and 9 respectively) by mentioning that G'd placed Adam in גן עדן, is to make it clear that גן עדן had been created specifically in Adam's honour, in order to place him there. After having given us this information the Torah continues and tells us that G'd made all kinds of trees grow from the soil, that these trees looked attractive and were good as food, that G'd made rivers and the function of those rivers which emanated from גן עדן. The Torah then resumes its narrative about man in verse 15, telling us that G'd placed Adam there and assigned a function to him. The Torah repeats that G'd placed man in גן עדן only to confirm that the first time this was mentioned it was only to tell us that G'd had planted גן עדן in man's honour. Had this fact been mentioned only once we would have thought that G'd intended this garden also for other creatures, such as His angels, and that man was placed there temporarily. We would have thought that after man's expulsion, the garden would have remained as be a home for other creatures and for holy spirits. The Torah therefore is at pains to make us understand that the garden was planted exclusively for man's sake and awaits man's return at a suitable time in the future and that no other creature inhabits it in the meantime.