Answer 1
The source is: Talmud, Yevamot 47. (Verses are quoted there, but they're not explicit.)
Answer 2
Strictly speaking, there is no biblical mandate (as in "Thou shalt not proselytize") in any particular biblical verse. There is also no verse in the Jewish Bible commanding proselytization, unlike the New Testament which is loaded with exhortations to spread the gospel. As a result, Jews had the "permission" to convert, but no compulsion to do so. The prohibitions therefore are assembled from several distinct concepts in the Torah and put together by the Rabbis outside of the Written Torah, in the Oral Torah. (This is the Talmud section discussed in Answer 1.) The Written Torah passages of note are all quoted at the bottom of the answer for reference.
The first, which is cited in Exodus 19:6 is that the Jews will be a holy nation. This creates a unique status for Jews that is separate and apart from others. This is further compounded by Exodus 23:33 where it is made clear that the customs of foreigners will negatively affect the belief and actions of the Jewish population. This promotes an idea of limited interaction with non-Jews and limited absorption of their ideals or customs.
The second, which is cited in Deuteronomy 7:9, is that Judaism is not a religion in the same way as Christianity is. Judaism is first and foremost a covenant or agreement. That agreement has activities and beliefs associated with it, but the beliefs come from the nature of the covenant. A Jew is required to be Jewish and most Jews are happy to be compelled in this way, but this changes the dynamic of the belief system. Christianity holds that a person is not in any way "bound" to be Christian in a legal sense, but chooses Christianity.
The third is that punishments for defying the Divine Covenant are quite severe. Numbers 15:30 makes clear that chooses to violate the covenant should be excommunicated. Understandably the enforcement of this penalty is restricted in the Mishnah and Talmud (due to necessary evidence etc.), but the sentiment that abrogation or failure to act properly merits as severe response shows how faithfully each Jew is required to observe the Law.
Historically, most religions that have proselytized have become the national religions of countries and created laws that made religious conversion a very important way to gain power and rights. As a result, it is likely that more people converted to Christianity, Islam, Hinduism, and Buddhism in order to gain political privileges, avoid economic penalties, and to avoid being murdered for their beliefs (presumably not the dominant religion) if they did not hold them strongly enough. This creates many members of the faith whose beliefs are not pure. Of course, being a proselytizing religion does not require this conduct, but it happens incredibly often.
Since Judaism treats the religion like a contract, individuals who may have converted for less than proper motives and proceed to break the promises they made are placed in an unenviable position. Judaism does not hold that all of the world should be Jewish, just God-fearing, which is far easier. Therefore, it holds back from actively proselytizing to avoid this problem. This is contrary to Christianity where conversion to Christianity is what allows a person to achieve salvation. In Judaism, a person can achieve a place in the World to Come by being a Righteous Gentile with fewer requirements and an easier time. Proselytizing would actually worsen the targeted individual's likelihood of partaking of the World to Come unless he was seriously interested in taking on the mantle. It is for these more serious individuals that Judaism is open.
Additionally, Jews avoid proselytizing because they know how annoying and obnoxious it is when others do it. Jews are taught to treat all people with dignity and respect, so they would not visit on others what is bothersome to them.
Biblical Verses (all NIV): [It is also worth noting that there are multiple iterations of these verses throughout the Written Torah. For example, Exodus 19:6 has the same general content as Leviticus 19:1-2.]
Exodus 19:6: 6 you [Israelites] will be for me a kingdom of priests and a holy nation.' These are the words you are to speak to the Israelites."
Exodus 23:33: 33 Do not let them [other nations] live in your land or they will cause you to sin against me, because the worship of their gods will certainly be a snare to you."
Numbers 15:30: 30 "'But anyone who sins defiantly, whether native-born or foreigner, blasphemes the Lord and must be cut off from the people of Israel.
Deuteronomy 7:9: 9 Know therefore that the Lord your God is God; he is the faithful God, keeping his covenant of love to a thousand generations of those who love him and keep his commandments.
There is no prohibition against wearing jewelry in Judaism.
Against Black advancement, immigration, Catholicism, and Judaism and for white power and alcohol prohibition.
Any woman can... But they are not supposed to. There is a Biblical prohibition against wearing items of clothing which are meant for the opposite gender.
There are many different prohibitions in Judaism; the most famous is the prohibition against eating any meat derived from a pig.
Law Enforcement Against Prohibition was created in 2002.
Association Against the Prohibition Amendment was created in 1918.
for and against the prohibition of internally generated goodwill?
Republican Citizens Committee Against National Prohibition was created in 1932.
There is no prohibition against marrying your cousin in Judaism, but most Jews, especially of European descent, tend to avoid this if only because it raises the probability of genetic diseases.
There can be. There is no Biblical prohibition against this, but ususally a day is selected that is most easily attended by friends and family, especially those who have to work or travel some distance. That day often is Saturday.
People who enjoyed a drink.
Many religions have a prohibition against alcohol (for example, Bahá'ís, Muslims, some Christians); some have a prohibition against eating meat in general; some have a prohibition against specific meats (for example, Jews and Muslims have a prohibition against eating pork - and Jews have various additional food-related prohibitions).