If some of the stitching around the base of the ‘titura’ (i.e. the large square under the cubed ‘bayis’) tears, the tefillin must be fixed, particularly if three or more stitches tear. In the event that no other tefillin are available, tefillin with torn stitching may be worn in the interim, until they can be repaired.
The ‘retzuos’ (straps)
Like the ‘batim’, the ‘retzuos’ must be made of the hide of a kosher animal, and the tanning and processing of the hide must be ‘lishmah’ (i.e. for the express purpose of the mitzvah). In fact, this requirement is even stricter for the ‘retzuos’ than for the ‘batim’, as we can infer from a previous lesson (quoted from the “MBY Archives”):
The hide must have been processed – from the point of tanning – for the sake of making tefillin. (Note: There are grounds for a leniency in certain cases with regard to the hide for the ‘batim’ only.) By this last note, the halacha implies that there are no such grounds for leniency with respect to the hide of the ‘retzuos’!
It is crucial also that the ‘batim’ be painted black, at all times (using special tefillin paint)! The paint need cover only the side which faces away from the body – i.e. the top side - (Ed: Although of late, I have observed that some people have begun to “beautify” the mitzvah by painting the underside as well – mine are not.)
Here is an important question: Does the paint have to be applied ‘lishmah’ (for the express purpose of the mitzvah), the same way that the processing of the hide must be done?
Answer: According to all opinions, yes. Whether or not the failure to have those specific thoughts in mind when applying the paint - or even “touching it up” - would invalidate the tefillin is subject to a disagreement among the authorities. Here’s what you do: whenever you touch up the blackness of your ‘retzuos’ with tefillin paint or a tefillin marker, make the following declaration before you begin: ‘L’shem kedushas tefillin’ (i.e. I am doing this with the holiness of tefillin in mind! If you do this, you will not have a problem!