It is known that the midos represent parts of the body (for example, Chesed is represents the right hand, Gevurah the left hand, Chachmah, Binah Daas represent the brain, and Netzach Hod, the two legs. Tiferes, Chazal tell us, is the body (the trunk of the body). Orach l'Chaim (Vayeitzei ויחלום י"א ה"ד) of Zlotchev zy'a explains that the body is called Tiferes because Tiferes means that Hashem has pleasure from us, as it states (Yeshayah 49:3) אתפאר בך אשר ישראל אתה עבדי, "You are my servant, Yisrael, in whom I take glory." The reason Hashem takes pride and joy in us is because of our human body. He writes, "I heard from Rebbe Dov Ber zt'l (the magid of Mezritzh) that Tiferes is called גופא body (introduction to Tikunei Zohar), because Hashem Yisbarach isn't מתפאר proud with his malachim and serafim who serve Him, because they must serve Him, and they don't have a yetzer hara or free choice. But Hashem Yisbarach praises himself with man who is clothed in a human body and has the free will to do as he desires. When he serves Hashem, this creates Tiferes, Hashem's pride."
The Baal HaTanya on Gashmiyus
The Baal HaTanya (Torah Or) concludes that if a person fasts for several days and has no strength, and can't say even one chapter of Tehillim, and the like. However, when he puts some food into his mouth, his strength will immediately return, and he can praise Hashem. So, we see that gashmiyus matters give a person strength to serve Hashem. Is there anything more precious to Hashem, that a davar gashmi (an item of this world) should be raised to sing to Hashem and to serve Him?!
Someone asked the Chazon Ish zt'l about a very special bachur, a masmid, a talmid chacham, with sterling middos. He told the Chazon Ish, "It looks like he doesn't even have a yetzer hara." The Chazon Ish replied, "Then he is a baal mum (flawed)." Because, as a rule, a person should have a yetzer hara. That's what makes his avodas Hashem precious to Hashem.
A Parable of the Singing Bird
Consider the following mashal (the Baal HaTanya tells a similar mashal in Torah Or, t'l, Vayishlach ה"ד הקרבנות והנה regarding a bird that speaks):
A wealthy, powerful king had many musicians and singers. They would play and sing before him, and the king had much pleasure from them. But mostly, the king would listen to his pet bird, which was trained to sing. All birds, by nature, can whistle a few notes, but this bird was able to sing real songs and carry a tune.
One of his professional singers said to the king, "I sing better than your bird. Why does the king prefer the bird's singing over mine?"
The king replied, "You sing beautifully, but this bird is a novelty and one of its kind. It is the only bird in the world that can sing songs. That's why I prefer listening to the birds' singing over the best singers and musicians."
The malachim sing better than us, and they serve Hashem with far more fear, love, and perfection than we can, but malachim don't have a yetzer hara, and they don't have hatred (see Shabbos 89a). Therefore, it is no chidush that they can sing before Hashem. But we are human beings, and the "yetzer hara becomes stronger over us each day" (see Succah 52b), to prevent us from doing avodas Hashem. Yet we are strong and we don't listen to the yetzer hara, and we serve our Creator. This makes a much greater nachas ruach for our Father in heaven.
