וַיֶּאֱסֹ֥ף אֹתָ֛ם אֶל־מִשְׁמָ֖ר שְׁלֹ֥שֶׁת יָמִֽים׃
그들을 다 함께 삼일을 가두었더라
Rashi
and the evening depart When will it become light and when will the time of arising come, and when will the evening depart? [The word מדד ] is an expression of (Gen. 31:40) “and sleep was banished (ותדד).” The “mem” is a defective radical, as in מאמר, statement; משמר, watch.
Chizkuni
לשלשת ימים, according to the plain meaning of these words the meaning is: “in anticipation of the third day.” According to the plain meaning, Moses did not add an additional day of preparation (sanctification) as suggested by some scholars. Other examples of a similar formulation in the Bible as here are Genesis 42,17: ויאסוף אותם אל משמר שלשת ימים, “Joseph put them in jail for three days.” Or, in the verse following: ויאמר אליהם יוסף ביום השלישי, “Joseph said to them on the third day;” or Genesis 40,19: בעוד שלשת ימים, “within another three days;” and in the verse following: ויהי ביום השלישי, “it was on the third day;” or Exodus 19,16: ויהי ביום השלישי, “it was on the third day;” there are numerous other examples.
Rav Hirsch
(21-34) Alle diese Verhandlungen waren wohl während der drei Tage ihrer Haft zwischen ihnen und Josef vorgegangen.