Devarim(14:2):Because you are a holy people to the L‑rd your G‑d and G‑d has chosen you to be His treasured people from all the nations that are on the face of the earth.
Inherently kind and sensitive to others
Yevamosh(79a): There are three distinguishing characteristics of the Jewish people. They are merciful, bashful and kind to others. They are merciful as is stated in Devarim (13:18):”…that G‑d should give you mercy [to be merciful to others – Rashi Beitza 32b] and be merciful to you and multiply you.” They are bashful as is stated in Shemos (20:17), “That His fear be before your faces.” They are kind to others as it is stated in Bereishis 18:19): “That Avraham may command his children and his household after him...” Whoever has these charcteristics deserves to be attached to this people.
Torah was given to Jews because they are aggressive and stubborn
Beitzah(25b): Why was the Torah given to Israel? Because they are aggressive and stubborn… If the Torah had not been given to Israel no nation or tongue could withstand them…
Rashi(Beitzah 25b): The Torah was given to the Jews because they are overly aggressive and the Torah serves to moderate their energy and subdue their heart…
Netzach Yisroel 14) I have already explained with clear proofs that the soul is the dominate factor in the nature of the Jew. For example, being stiff necked is one of the bad qualities that Jews have. Practically speaking that means that Jews refuse to accept chastisement and will not listen to corrective advise. This is in fact because they are not essential materialistic. Only something which is materialistic is readily altered. Consequently Jews are very resistant to change and will not accept the advice of others. Furthermore the (Beitzah 25b) states that they are the most aggressive and pushy people. That is because they have the power associated with being the defining figure that is separate and distinct from the readily altered material. In contrast the non‑Jews readily change their ways and readily accept correction. The Yerushalmi (Sanhedrin 11:5) therefore explains that Yonah did not want to go on a mission to Nineveh because he knew that this people would readily repent after hearing his chastisement. This would reflect badly on the Jews who stubbornly resisted repenting…
Shemos Rabbah (42:9): What is meant by saying that the Jews are a stiff‑necked people (Shemos 32:9)? R. Judah b. Poloyah said: They deserve to be beheaded. R. Jakim said: There are three who are inherently arrogant and overly self‑confident. The dog amongst animals, the rooster amongst birds, and the Jews amongst the nations. R. Yitzchok b. Redifa said in the name of R. Ammi: You think that this is said disparagingly, but it is really a praise. It means that a Jew will more readily be hanged then give up Judaism. R. Abin said: To this very day Israelites in the Diaspora are called the stiff‑necked people. R. Nahmani said: To prove to you that they are stiff‑necked, you should note that when G‑d was about to give them the Torah it says, On the morning of the third day, there were thunder and lightning and a thick cloud upon the mountain, and the sound of a very loud shofar (Shemos 14:16). G‑d said: ‘I will show them all My miracles, and I only hope that it will be of some purpose.’
Shemos Rabbah(36:1): Why did Yermiyahu (11:16) describe the Jewish people as: “A leafy olive tree, fair with beautiful fruit?” The lesson is that just as the olive …is taken off the tree and beaten and then it is taken to vat and placed in a grinding-mill and then it is ground and afterwards tied with ropes. Then finally when stones are put on them they produce oil. It is similar with Israel. The idolaters come and beat them from place to place, imprison them, put them in chains, surround them with guards and only then does Israel repent their sins and G‑d answers them. How do we know this? Because it says in Shemos (2:23) that the Jews sighed and G‑d heard their groaning… Similarly in Devarim (4:30), “In your distress…because G‑d is a merciful G‑d.” That is why the Jews are described as “A leafy olive tree, fair with beautiful fruit.”..
Reishis Chochma (Yira 14): Concerning the service of G‑d one should not have fear or embarrassment as it says in Avos(5:20) be as chutzpidik as a leopard to do the will of our Father in Heaven. Nevertheless it is necessary to be shy and self effacing with people when in worldly matters which are not connected to religious issues. Similarly one needs to have proper fear and respect for Torah sages...
Wise and intelligent
Devarim(4:6): 6. Keep therefore and do them; for this is your wisdom and your understanding in the sight of the nations, who, when they shall hear all these statutes, shall say, Surely this great nation is a wise and understanding people.
Shabbos(75a): R. Simeon b. Pazzi said in the name of R. Joshua b. Levi on the authority of Bar Kappara: He who knows how to calculate the cycles and planetary courses, but does not, of him Scripture saith, but they regard not the work of the Lord, neither have they considered the operation of his hands. R. Samuel b. Nahmani said in R. Johanan's name: How do we know that it is one's duty to calculate the cycles and planetary courses? Because it is written, for this is your wisdom and understanding in the sight of the peoples: what wisdom and understanding is in the sight of the peoples? Say, that it is the science of cycles and planets.
Not inherently superior to other people
Ohr HaChaim (Shemos18:21): Why did Yisro deserve being the source of the information about forming the judicial system - especially when it implies - chas v'shalom - the ignorance of G-d's people prior to his suggestions? The Ohr HaChaim answers is that G-d wanted to teach the Jewish people a fundamental lesson for all generations. The lesson being that there are among the nations of the world men of great intelligence and understanding and these nations have awareness of important and valuable information. G-d's intent was to show through Yisro that the election of the Jews was not because their knowledge and insight was greater than other nations. They were not chosen because of their superior wisdom and knowledge. Their election was the result of G-d's supreme kindness and His love of the Avos. This explanation is more appropriate according to the view that Yisro came prior to the Revelation at Sinai. Accordingly G-d's message was that even though there are amongst the Nations greater wise men than amongst the Jews - the Jews were nevertheless chosen. We are therefore to praise Him for choosing us because of his Kindness. However, even according to the view that Yisro came after the Revelation at Sinai - a similar lesson can be learned by the fact that Yisro is mentioned in the sequence of events of the Torah prior to the giving of the Torah.
Treasured and Beloved of G‑d
Devarim(7:6-8): For you are a holy people to the L‑rd your G‑d. The L‑rd your G‑d has chosen you to be a special people to Himself - distinguished from all the nations that are on the face of the earth. G‑d did not desire you and chose you because you were more numerous than all the other nations - because in fact you were the smallest of all nations. Rather it was because of His love for you and to keep His promise which He had sworn to your forefathers that G‑d has taken you out with a strong hand and redeemed you from the house of slavery from the hand of Pharaoh the king of Egypt.
Kuzari(1:95): 1) By the time the Jewish people had become a nation, with people such as Moshe, Aharon, Miriam, Betzalel, Yehoshua etc. even though there were sinners who were hated by God [for what they did], there is no doubt that they too were segula for from their root and nature they were segula, and in the future they would give birth to children who would be segula. 2) The children of Yaakov were all segula and were distinguished from the rest of mankind in their godly characteristics, for He made them as a distinct, angelic species [he actually writes, that asking why non-Jews cannot be like Jews is like asking why animals can't talk]
Ramban (Devarim 7:8): And He chose you – from all the nations that you should be special and His inheritance because the choice means distinguishing a part from the rest. The Torah explains that this choice was the result of G‑d’s love for you. He saw that you were fitting to be beloved before Him and to be beloved more than all the other nations. The Torah does not mention the reason for being chosen because the One who chose to love is known to make his His beloved bear all the suffering that comes from Him. Israel is more fitting of this suffering than all the other nations. This is indicated in Beitza (25b): There are three who are distinguished by their strength – one is Israel amongst the nations. That is because they are able to withstrand their trials and tribulations. As it says in Shemos Rabbah (42:9): Either be a Jew or be crucified. The meaning of “I chose you” means for the sake of your forefathers that matters devoped until that they were sworn that their descendants would be chosen. That was so that the sins of their descendants would not nullify the promise. Consequently G‑d took you out of the land of Egypt with a strong hand.