"And G-d spoke to Moshe, saying: Speak to Aharon and to his sons, saying,
'so shall you bless the children of Israel...'" [6:22-23]
In the beginning of Parshas Mattos (Num. 30:2), the commentator Rashi
quotes the Medrash (Sifri) which says "Moshe prophesied with 'So says
HaShem, ("At about midnight...") (Ex. 11:4)', and the other prophets also
prophesied with 'So says HaShem', but Moshe had the additional ability to
prophecy with 'This is the statement'."
The Torah V'HaMitzvah explains as follows: every prophet could "see" G-d
with an "unclear" vision, meaning that the prophet became G-d's appointed
representative (Shaliach) to deliver the Divine message in his own words.
We see that Moshe as an individual could also prophecy in this way: before
Israel left Egypt, he said "so says HaShem, 'At about midnight...'", and
when Israel fell from their heights during the incident of the Golden Calf,
Moshe again used the language of "so says HaShem" when speaking to the
tribe of Levi (Ex. 32:27).
Moshe, however, reached a unique level as leader of the Nation of Israel
when G-d gave the Torah. He also could have a "clear" vision, a more
absolute contact with HaShem. In those cases, Moshe was not G-d's
representative, delivering a message, but rather it was as if G-d Himself
was speaking. "The Divine Presence spoke from within his throat."
In Maimonides' introduction to the Mishnah, Seder Z'raim, he says that when
HaShem tells us good news (for those familiar with non-Jewish preachers,
forgive me the terminology - would you prefer "good tidings?") about our
future by way of a prophet, it is impossible for it not to actually happen,
for otherwise prophecy could never be substantiated. We would worry that
every prophet was false. Thus the Talmud says (Brachos 7a) "every statement
which came from HaShem for good, even conditionally, He will never retract."
On the other hand, we see that when HaShem Himself promised our forefather
Yaakov that "I will be with you and guard you wherever you go," nonetheless
Yaakov "was extremely fearful and his courage left him," because, according
to our Sages (Brachos 4a), he was afraid that because of his sins he was no
longer worthy of protection. The Rambam (Maimonides) explains that this can
only occur between HaShem and the prophet directly, for the prophet himself
(or herself) will of course not come to doubt either G-d's existence or his
own prophecy as a result. But concerning a prophecy given over (by way of a
prophet) to the people at large, we would be unable to rely upon or trust
in prophecy if the words of even true prophets were to never come to pass.
Rabbi Zvi Elimelech Hertzberg zt"l uses all of the above to explain the
unusual language of the verses in our parsha. G-d tells Moshe, "Speak" to
the Cohanim, the Priests, using the same root (Davar) as the word for
"statement." But what shall Moshe say? "so shall you bless..." using the
language of "so" HaShem says, the language used by the prophets as G-d's
representatives. What the Cohanim then say is G-d's message: that G-d
should bless us and guard us, that He should show us mercy and give us
peace, can then never be retracted. "Let them place my name upon the
Children of Israel, and I shall bless them" (Num. 6:27) - this blessing
must certainly come to pass!