The answer to this question is that your friend is incorrect, as are you yourself, insomuch as you apply yourself exclusively to the Qur'an, whereas Allah, blessed be He, points you in another direction, within the Qur'an, and this is readily apparent. Amongst the Shia, some claim that the word transliterated as imam appears a dozen times within the Qur'an. This is true, but somewhat misleading, when the meaning of this form also includes meanings other than leader/s (7x); guide (2x), record/register (2x), highway (1x). Some people note that the sons of Jacob are worthy of mention, being twelve (Genesis29:31-30:24, 35:16-18,22-26). If they were classed as imams then this would make some kind of a case, on a comparative basis. This is not the case though, however we look further, and consider the twelve apostles of Yeshua ben Miriam (Matthew10:2-4/Mark3:14-19/Luke6:13-16, John6:67-S3:52-3/61:14-John6:68-71). So we see numbers of note appearing, such as twelve, but why not seven, or nineteen? There is no firm case from these matters. Yet the pro-Shia site, Al-Islam.org, under the header of The Holy Qur'an and the Pure Imams, does cite two verses which uphold the claim of twelves imams for the house of Ishmael (S16:43, 21:7). Those verses are a recommendation, for men of reason who seek confirmation, to seek the words of those who were given the scripture to remind mankind of that which was before them, in dramatic examples. Then the verse, which stands alone in the remnant of the Abrahamic Scroll reads thus: Yishmael...He shall bring forth twelve imams, and I will make him a great nation (Gen.17:20). The word that I have translated as imams comes from the primitive Hebrew root nun-samech-heh, which means that carried off, taken, supported, or exalted. The word is transformed to the Hebrew nun-shin-aleph, meaning vapour/rising, exalted, prince, chief, leader, captain. Now, the common thought amongst the Jews and Christians points to this matter of prophecy being fulfilled in that period in the manner of the sons of Jacob (Gen.25:16). Then compare this to the word of Allah; That is a nation which has passed on; it will have what it earned, and you will have what you earned...(S2:141), as regards the descendants of Abraham, Yitzhak, and Jacob. So, we see a harmony now between the definitions of a nation, within the Judeo-Christian text, and that of the Qur'an. Twelve leaders emerged for the bani Yishrael (S5:12). Even if this word in Arabic (naqib) was read in Hebrew (naqab), it could still be read as appointed ones. Twelve leaders emerged for the Netzerim (S61:14). Then, did twelve leaders emerge for the children of Ishmael, or was it more, or was it less?