The Midrash Tanchuma writes that Moshe foresaw the destruction of the Mikdash which rendered the mitzvah of bikurim impossible to fulfill; he therefore instituted davening three times a day in its place. Why was Moshe concerned over the loss of bikurim more than any other mitzvah? And wasn't davening already instituted by the Avos (Brachos 26b)?
1. The second tochacha of the Torah corresponds (writes the Ramban) to the destruction of the second Mikdash. The pasuk tells us that the reason for tochacha is "tachas asher lo avadita es Hashem Elokecha b'simcha u'btuv leivav," there was a lack of simcha and joy in avodas Hashem. Yet, Chazal tell us (Yoma 10) that the second Mikdash was destroyed for the sin of sinas chinam, not lack of joy?
The Shem m'Shmuel answers that both of these sins share the same common denominator. A person who is is doing mitzvos without really wanting to will rush through them with a superficial, rote performance; simcha comes only to a person who loves what he/she is doing and immerses his/her entire personality in their work. The key to ahavas Yisrael is overlooking the superficial differences that seperate us all and focussing instead on the shared G-dly spark within each of us (Tanya ch 32, Pri Tzadik, P'Kedoshim). A person who tries to get away with being frum on a superficial level without putting his/her heart into it, a person who wants to be perceived by others and judged by this superficial veneer, is a person who judges others the same way, looking at superficial veneer and the many differences between people instead of the pnimiyus of our shared humanity.
The parsha of bikuim ends, "V'samachta b'chol hatov..." Hashem encourages us to relish the simcha of bikurim. Why is this mitzvah in particular characterized by simcha? I think we can get to the answer if we think about the meaning and cost of the little fruit basket the farmer brings. You can fulfill bikurim with a few dollars worth of fruit, but what makes the mitzvah special is that those fruits are the first fruits -- there is an emotional chord struck in the farmer, something that stirs in his pnimiyus, when he finally sees what his labor has brought to being. It's not just a fruit basket the farmer brings, but it is all the emotions beneath the surface connected with thanks for another successful harvest. Bikurim is a mitzvah of simcha because it embodies the idea of finding meaning in pnimiyus instead of superficials.
When Moshe saw the loss of the Mikdash because of the lack of simcha, because of sinas chinam, he saw a society focussed on external trappings and superficiality. He saw in particular our loss of bikurim, the mitzvah that reminds us of the well of meaning that exists behind the superficiality of just a little sacrifice of fruit.
2. The parsha of bikurim is followed by the parsha of viduy ma'aser. The focus of the entire viduy is the farmer's actions -- he used ma'aser only as food, he seperated his tithes in the right order, he recited a bracha, he gave away his terumos and ma'asros to make others happy, etc. -- the farmer sounds almost boastful that he got everything right and did what he was supposed to. The conclusion sounds like a quid pro quo request -- "G-d, I did what you asked, now you do what I ask and provide a blessing."
Contrast that with the parsha of bikurim which speaks not of anything done by the farmer, but only of the help G-d gives -- not just G-d's help in bringing the crop to fruition, but of the help which G-d has given the Jewish people throughout history. As opposed to viduy ma'aser where we introduce our supplication by recounting our own merits, in the parsha of bikurim we try to ellicit G-d's continued help by reciting his "merits", so to speak, meaning the chessed he has performed for us even when we may not have deserved it and even when there was nothing done on our part.
"V'anisa v'amarta" -- the Tiferes Shlomo explains that "v'anisa" here does not mean "to answer", but is from the same root as "ani", a poor person. Bikurim is "tefilah l'ani ki ya'atof," the prayer of one who is poor in deeds but looks to G-d's charity.
The tefilos of the Avos were the tefilos of those who achieved the pinnacle of closeness with G-d. The tefilah of vidy ma'aser is the tefilah of someone who can point to the fact that it looks like they have done everything right. But what if there is nothing we can point to on the surface that gives us credibility to ask anything of G-d? What if there is no deeds that we can use to gain entrance for our prayers?
What we need is tefilah l'ani, tefilah which ellicits Hashem's mercy based not on deeds, but based on the fact that b'pnimiyus there is an inextinguishable bond with Hashem that remains even when on the surface we have no other merits. This is the tefilah of "anisa v'amarta" of the bikurim which Moshe found a way to preserve for us even when all else was destroyed. Our obsession with superficialities led to the Mikdash's ruin; our recovery of the spirit of bikurim through heartfelt tefilah that stems from the pnimiyus of our souls can lead to its being rebuilt.