Rashi: He mixed a drink for them; he made their Ru'ach crooked. "Masach" is like "Maschah Yeinah" (Mishlei 9:2). Mixing a drink in a barrel, until it has the proper taste, is called Masach.

Radak: He confused their counsel and destroyed their Chachmah. Masach is mixing, like "b'Yayin Masachti" (Mishlei 9:5).

Malbim: He put in them a spirit of confusion and insanity, like one who mixes wine so it will be pleasant to drink. Egypt drank from this intoxicating wine, and became drunk.

Rashi: It is the name of an illness of insanity.

Radak: It is from the root Avah - Na'avah Lev (a crooked heart).

Refer to 19:13:3:1-2.

Radak: Sometimes the verse uses the feminine for the assembly, and sometimes it uses the masculine for the nation.

Radak citing Targum Yonasan: He errs in his thoughts and tramples in his liability. I.e. he does not know what to do, and vomits, and afterwards rolls in his vomit.

Malbim: A drunkard strays to return to drink his vomit, which his innards and stomach expelled, for it cannot bear it. He thinks that it is wine, and he drinks it. So [the officers] misled Egypt to do deeds against their nature, for which the land will vomit them out, and it cannot contain them ¹ .