What are the connotations of the word "Achorai"?
Rashi: It refers to the knot of Hashem's Tefilin shel Rosh. 1
Ramban: Refer to 33:19:1:2.
Targum Yonasan: It refers to Hashem's Tefilin Shel Yad. 2
Rosh: It is what Hashem leaves after passing - 'the air of the world'.
Toras Moshe: It is understanding at the end Hashem's purpose in retrospect.
What did Hashem mean when He said "Vera'isa es Achorai, u'Fanai Lo Yera'u'?
Seforno: Hashem showed Moshe Hashem's workings that are below Him - but not how He bestows existence upon all His creations from His own Existence. 1
Rashbam: After Hashem passed Moshe and made a covenant with him, 2 he would be allowed to see - but not before (Hashem's Face).
Da'as Zekenim: He meant that, like someone who sees his friend from the back, he will not able to discern His features.
Toras Moshe: He meant that one cannot comprehend why Hashem does things at the time that He does them, and it is only afterwards, in hindsight, that one can understand His purpose.