His trained servants. It is written "his trained one," referring to Eliezer whom he trained to observe the mitzvos...Trouble is, that isn't what the verse says. The MT has חניכיו/his trained oneS.
My uneducated hunch is that Rashi's chumash departed from the MT on this spot. This is also my uneducated way of explaining Rashi's mysterious comment on Numbers 15:39 where he produces a gematriah on the word "tzitzit", based on a spelling that is never used in the MT. I think that in both cases, Rashi was using a text that didn't match the MT letter-for-letter.
Alternativly, its possible that this strange comment didn't originate with Rashi. That appears to be the view of the Sapirstein Rashi where the bit about the "trained one" is excluded. We're told in a footnote that the comment is found in just two of the four best-known Rashi manuscripts, leading the author to doubt its provenance.