When reciting Baruch SheAmar we hold the front Tzitzit in the right hand. When we recite the Shemah we hold the Tzitzit between the 4th and 5th fingers of the left hand. Why the difference of hands? What is the derivation and meaning of these customs?
Shalom, Thank you for your question. I'm not sure that I will be able to answer it to your complete satisfaction, as the roots of these customs lie in the kabbala – and some of these practices lie outside an ability to give them a clear explination. None the less – the source for holding the two tzitzit during Baruch Shema is found in the Magen Avraham (Shulchan Aruch, Orech Haim, 51, Magen Avraham 1). There he quotes the Ari HaKadosh. The reason why we hold just the two tzitzit there is because "the light of the mitzvah of the two tzitzit from in front of him surround him from Baruch Shema until the blessings of the Shema, when the 'surrounding light' [Or HaMakif] is added from the two back tzitzit". In the work Or Tzadikim he writes to hold the two tzitzit in one'e right hand. The responsa of Zichron Yehudah (chapter 9) points out that there are 10 praises in Baruch Sheama, which relate to the 10 sayings G-d used to create the world, and the 10 knots in the two tzitzit we hold. (See Piskay Tshuvot 51, 3 and the footnote there). As to the Shema, there are several different customs – with some people holding all four tzitzits as per the Ari above), and some holding only the front two (as per the simple reading of the Shulchan Aruch Orech Haim 24). According to the kaballah the four strings are held at first in the left hand, as the right hand is used to cover the eyes with. They are held between the 4th and 5th finger, as recorded in the Eshel Avraham in the name of the Yam Shel Sholmo, where he writes that there is "a very deep secret in this matter". Only later, when one reaches the last paragraph of the Shema, does one transfer them to the right hand (with the "roots" of the tzitztit still in the left hand). I hope this is of some help to you – even if we did not manage to reveal all the hidden mysteries of this custom. Blessings.