וְאִ֗ישׁ אֲשֶׁ֨ר יִשְׁכַּ֤ב אֶת־זָכָר֙ מִשְׁכְּבֵ֣י אִשָּׁ֔ה תּוֹעֵבָ֥ה עָשׂ֖וּ שְׁנֵיהֶ֑ם מ֥וֹת יוּמָ֖תוּ דְּמֵיהֶ֥ם בָּֽם׃
And if a man lie with mankind, as with womankind, both of them have committed abomination: they shall surely be put to death; their blood shall be upon them.
Rashi on Leviticus
משכבי אשה means he inserts as a brush into a tube [i.e. in the manner of marital intercourse].
Siftei Chakhamim
One inserts. Because if not so, why write “in the same manner as with a woman?” Is there another way to lie with a male that the verse has to say “in the same manner as with a woman” in order to exclude this other way of lying?
Chizkuni
משכבי אשה, intercourse in the full sense of the word, not fondling or premature withdrawal of either party’s male organ.