In the Halachot of Tefilin, there is a discussion whether one must make a new Beracha if he puts on a second pair of Tefilin. Take for example the following case. A person comes to Shul without his Tefilin, so he borrows a pair and makes a Beracha on them. During the Tefila, he finds his own Tefilin, which are more Mehudar, and wants to put them on instead. Does he have to make a new Beracha of "Lhaniah Tefilin" or not?
Ostensibly, this should be a simple question. The Ben Ish Hai (Rav Yosef Haim of Baghdad, 1833-1909) already established in the Halachot of Sisit that if one wants to put on a different Tallit, he must make a new Beracha, even if he had specific intent to switch to the new Tallit when making the first Beracha. This ruling is accepted by Hacham Ovadia, and seemingly, the case of Tefilin should be no different. He should have to make a new Beracha.
However, the Zera Emmet distinguished between the case of Tefilin and the Tallit, and ruled that one should NOT make a new Beracha on the Tefilin. He argued that there is a fundamental difference in the nature of the obligation of these two Misvot. Technically, there is no obligation to wear a four-cornered garment. Rather, if one chooses to wear it, he must tie Sisit. Therefore, once a person takes off the first Tallit, he has finished the Misva, and there is no obligation to continue doing so. When he put on a second Tallit, it is new Misva and requires a new Beracha. On the other hand, there is an active commandment to wear Tefilin for as much of the day as possible; the Misva is continuous. Therefore, even after he removes the first pair, his obligation continues. The second pair of Tefilin are a natural continuation of the first pair and do not need a new Beracha.
Hacham Ovadia, in Yabia Omer vol. 3, brings down the opinion of the Zera Emmet, which implies that he agrees. Nevertheless, Hacham David in his responsa "Osrot Yosef," printed in the back of Halacha Berura on Tefilin, writes that he found a ruling of the Sefer HaEshkol (R. Avraham b. Yishak, 12th Century, France) regarding Hilchot Mezuza, from which he derives his opinion regarding Tefilin. The Sefer HaEshkol rules that if one removed a Mezuza in order to replace it with a more Mehudar Mezuza, he must make a new Beracha. Hacham David reasons that if this is true regarding Mezuza, which is a constant Misva that cannot be fulfilled by merely placing it one the doorpost once a day, certainly it is true regarding the Misva of Tefilin, which can be fulfilled fundamentally by putting them on once a day. Based on this, Hacham David rules that one must recite a new Beracha on the second pair of Tefilin. He argues that if Hacham Ovadia would have seen this ruling of the Sefer HaEshkol, he would have retracted his ruling in accordance with the Zera Emmet.
The Halacha is in accordance with Hacham David. Nevertheless, it is preferable to avoid entering this dilemma in the first place. One should create an interruption between donning the two pairs of Tefilin, by taking a walk outside.
SUMMARY:
If one put on a second pair of Tefilin or Tallit, he must recite a new Beracha, even if he had intent to switch when making the original Beracha.
