We read last Shabbat parshat Toldot in which we find the famous statement in Bereshit 25:27
וְיַעֲקֹב֙ אִ֣ישׁ תָּ֔ם יֹשֵׁ֖ב אֹהָלִֽים
The mefarshim deals with the meaning of ישב אהלים, some like Rashi focuses more on the word "tents":
ישב אהלים DWELLING IN TENTS — the tent of Shem and the tent of Eber (Genesis Rabbah 63:10).
Others like Rabbi Abraham Ibn Ezra and RaSHbaM focus their explanation more on the combination of the words ישב אהלים : Ibn Ezra comments as follow:
And Jacob "stayed in the tents:" And it seems likely that its meaning is like "those who dwell in tents and amidst herds." (Gen. 4:20)
RaSHbaM comments as follow:
ישב אהלים, tending his father’s flocks as we explained already in connection with 4,20 ישב אהל ומקנה.
After a quick look at the main other mefarshim, it seems that nobody exactly questioned the fact that the Torah says ישב אהלים and not ישב באהלים.
What is the difference of meaning between ישב אהלים and ישב באהלים in biblical Hebrew?