When Moshe Rabbeinu chastises Yisrael for their shortcomings by mentioning places in which they sinned, he refers to two particular episodes with the wordsבין פארן ובין תפל ולבן . Rashi brings the Chazal that interprets these two mentions as follows; Paran refers to the chait of the Meraglim, and Tofel refers to the point in time when Yisrael complained about the manna from heaven which was the color of white. The meforshim ask that according to Rashi’s interpretation, the insertion of the two words of בין  (between) doesn’t seem to fit in this context.
The Keli Yakar answers this problem with his own interpretation of the word תפל in that it is referring to the sin of the עגל. We find many times that the word תפלה is used to express the sin of avodah zarah and this time is no exception. The worshipping of the Aigel was on the 17th day of Tammuz, the day that Moshe descended from Har Sinai and broke the two Luchos. The breaking of these stones had a lasting effect upon Klal Yisrael, for on that same date hundreds of years later, the stone walls of the Yerushalyim were also broken and penetrated.
Now we can understand the usage of the two בין in describing the two acts of Yisrael’s rebellion against Hashem. On the 17th of Tammuz we worshipped the Aigel and the Luchos were broken an event which is hinted in the word תפל . On the 9th of Av we sinned by listening to the report of the Meraglim and complained about entering Eretz Yisrael. When these two separate events happened on the dates of the calendar within a three week period from each other, these three weeks between the 17th of Tammuz the day of worshipping the Aigel, and the 9th of Av the chait of Meraglim transformed all of these 21 days into days of tragedy for Am Yisrael for all future generations. This is the 3 week period which the passuk refers to when it says (Aicha 1,3) כל רודפיה השיגוה בין המצרים all those who chase Yisrael found her vulnerable and attackable during this three week segment.
In essence Moshe Rabbeinu was reprimanding them on the rebellious events בין Tisha B’av and בין the 17th of Tammuz. He was instructing them to undergo teshuvah on these actions and their underlying causes, for if not, they for sure will be sent into galus during this same time period.
The chait of the Aigel was the turning of their backs to the reality of Hashgachas Hashem upon them. It was therefore a בין אדם לה’ lacking. The Meraglim was an event that was fostered by the שנאת חנם . This concept can be gleaned from the passuk (Devarim 1,27) that Yisrael spoke Lashon Harah on Hashem “It is because of Hashem’s hatred of us  that He redeemed us from Egypt in order to make us suffer by giving us Eretz Yisrael”. Rashi learns that the claim against Hashem for hating them was really the defense mechanism of projection for it was really they who hated Hashem. The Keli Yakar explains that their claim of Hashem’s hatred to them stemmed from their hatred to one another. Just like they were hated by their fellow man, so too it is conceivable that Hashem could hate them as well.
In short, according to this interpretation, it was the hatred from one Yid to another that caused them to believe in the report of the Meraglim which resulted in the tragedy of Tisha B’av. That is why we find that even during the days leading up to the first Churban we find that “sinas chinam” was prevalent amongst the leaders of Am Yisrael. In contrast, the downfall of the 9th of Av was because of the deterioration of בין אדם למקום.  
Had one of these fallouts been corrected by Klal Yisrael we might have been able to withhold the consequences of the Churban and galus. This time period has turned this nation into being anאבל , a mourner. The word אבל  is the acronym בין אדם לחבירו, בין אדם למקום . We lost both of our lines of defense. This can also be hinted in the two seemingly extra words of בין פארן ובין תפל that each event reflected its blemish on a particular relationship of the Jewish Nation. פארן was בין אדם לחבירו and תפל was בין אדם למקום.
We can now understand the passuk we read on ShabbasNachamuנחמונחמו עמי יאמר אלהיכם. The Navi relates a double comfort for Am Yisrael after the Churban. We can say the double comfort is for the blemishes that border the Three weeks. One was the 17th of Tammuz which was the breaking of the Luchos and the worship of the עגל corresponding to the blemish of our relationship with Hashem. The second was the 9th of Av the sin of the Meraglim and our hatred of one another which caused us to believe that Hashem hates us and therefore is sending us to EretzYisrael to suffer. This can also be the reason why the Navi used the word עמי instead of Yisrael. For the acronym of עם alludes to the two fallouts at the borders of the Three Weeks, the sin of the עגל and the sin of the מרגלים. For each failure and repair we will merit a נחמה . 

– Rav Brazil
Gut Shabbos