I first heard this d'var torah from my good friend Rabbi Chaim Brown around 16 years ago.
The Shev Shma’atsah in his hakdama has the following vort on this week’s parsha.
Rashi writes that "vayikchu li trumah" means "li-l’shmi", that the giving of the terumah must be done l’shma. The Shev Shma’atsah asks, why does this mitzvah need to be done l’shma more than any otehr mitzvah? By other mitzvos we find that we are told one should do them sh’lo lishma and eventually you will do them lishma.?
The Alshich asks, why does the Torah say "vayikchu li teruma", if the B’nei Yisroel gave the terumah to Hashem. It should have said "vayitnu li terumah". The Alshich answers that when B’nei Yisroel gave the terumah to HKBH, it is as if they are giving a present to an adam chashuv. The halacha is that if a woman tells a man to give a present to an adam chasuv, then she is married to the man thru the ha’na’ah she gets when the adam chashuv accepts the present. Therefore, when HKBH accepted the terumah, the B’nei Yisroel got ha’na’ah and it was as if they were really receiving a present from HKBH. That is why it says "vayikchu li teruma", because B’nei Yisroel really took from Hashem.
However, by the case of the adam chashuv if he will eventually return the present then thereis no hana’ah and the kidushin isn’t chal. Therefore, the answer of the Alshich only works if the terumah was given lishma. If the teruma was given sh’lo lishma (i.e. the B’nei Yisroel gave the terumah to receive something back) , then it is as if the adam chashuv (HKBH) returned the present. If HKBH returned the present then the B’nei Yisroel were not receiving any ha’na’ah from HKBH it it would no longer be "vayikchu li" but "vayitnu liu". This is why the teruma had to be totally lishma.
The Shev Shma’atsah in his hakdama has the following vort on this week’s parsha.
Rashi writes that "vayikchu li trumah" means "li-l’shmi", that the giving of the terumah must be done l’shma. The Shev Shma’atsah asks, why does this mitzvah need to be done l’shma more than any otehr mitzvah? By other mitzvos we find that we are told one should do them sh’lo lishma and eventually you will do them lishma.?
The Alshich asks, why does the Torah say "vayikchu li teruma", if the B’nei Yisroel gave the terumah to Hashem. It should have said "vayitnu li terumah". The Alshich answers that when B’nei Yisroel gave the terumah to HKBH, it is as if they are giving a present to an adam chashuv. The halacha is that if a woman tells a man to give a present to an adam chasuv, then she is married to the man thru the ha’na’ah she gets when the adam chashuv accepts the present. Therefore, when HKBH accepted the terumah, the B’nei Yisroel got ha’na’ah and it was as if they were really receiving a present from HKBH. That is why it says "vayikchu li teruma", because B’nei Yisroel really took from Hashem.
However, by the case of the adam chashuv if he will eventually return the present then thereis no hana’ah and the kidushin isn’t chal. Therefore, the answer of the Alshich only works if the terumah was given lishma. If the teruma was given sh’lo lishma (i.e. the B’nei Yisroel gave the terumah to receive something back) , then it is as if the adam chashuv (HKBH) returned the present. If HKBH returned the present then the B’nei Yisroel were not receiving any ha’na’ah from HKBH it it would no longer be "vayikchu li" but "vayitnu liu". This is why the teruma had to be totally lishma.