Which Tefillin should one wear if only one is available?

Question

I'm asking this as a multi-part question...

1 - Let's say one can obtain just one tefillin (say, he is poor, can afford to buy just one.) Which one should he obtain first - yad or rosh(hand or head)?

2 - Eventually, he can get the full set. But, for now, only one is available (say, shul happens to have a spare yad or a spare rosh.) Let's say, if he waits for the set, it will be after Kri'at Shema time, and ideally one should wear tefillin when reciting Shema. Should he wear the one that's available, or recite Shema on time without tefillin, and wait until the full set becomes available?

Answer 1

Rav Chaim Kanievsky was asked this question in Daas Noteh Hilchos Teffilin page 117. He answers that shel Rosh is preferable, but adds a tzorech iyun kitzas since the Mishna Brurah does not choose between the shel yad and shel rosh in a similar case. See footnote 329 which does bring the Yafeh Lalev that writes the shel Yad comes first since its mentioned in the Torah first,and the Shaarei Teshuvah writes that the shel Rosh comes first since it has more kedusha.

Regarding you second question it seems pashut that if one would miss krias Shema then he should certainly wear the one he has,but like it shows in the next question if krias shema won't be missed it seems better to wait for both, but see footnote 330.