Rashi on Genesis 26:26/רש"י על בראשית כ״ו:כ״ו

1ואחזת מרעהו —as the Targum renders it: וסיעת מרחמוחי which means a company formed from his friends, the מ meaning from סיעת ממאוהביו. There are some who explain that in מרעהו the מ is part of the noun מרע — just like (Judges 14:11) “Thirty companions (מרעים)” in the narrative of Samson — in order that the word ואחזת should be taken to be the construct state to מרעהו (the company of his friends). But it would not be a polite thing to speak thus of a king — the company of his friends — for if this were the meaning it would imply that he (Abimelech) took with him the whole company of his friends and that he had no more than one group of friends. For this reason it should be interpreted in the first way (that אחזת is not construct). And you need not be surprised at the ת of אחזת although the word is not in the construct state, for we have similar cases in Scripture: (Psalms 60:13) “help (עזרת) against the adversary”, and (Isaiah 51:21) “Drunken, (שכרת) but not with wine”.

2אחזת signifies a collection and band, and a band is so called because the people who constitute it are held נאחזין together.