The Poskim discuss whether or not it is permissible to stick one’s fingers in the cracks of the stones of the Kosel. We know that the Kosel is a remaining wall of Har Habayis and one may not enter the Har Habayis when one is a zav or baal keri. The question is based on the Rambam in Hilchos Bais Hamikdash 3:18 that discusses whether or not a partial entering is considered assur, meaning if only part of the body enters in a kodesh place. The Rambam says it is forbidden Mi’deRabbonon and the Ravad says it is assur Mi’deOraysa. The Chazon Ish was machmir. The Maharil Diskin and the Steipler agreed that it is forbidden. The Avnei Nezer disagreed. Reb Shlomo Zalman says in the name of Reb Tzvi Pesach Frank, that one need not be machmir. Reb Shloma Zalman was machmir for himself.
One of the reasons to be meikil is because the choma around the Har Habayis was not built in the kodesh part. A proof can be brought from the Mishna in Middos 2:1 that says the dimensions of Har Habayis was 500 amos by 500 amos. The Achronim have a safek whether the Choma was outside the 500 x 500 or inside of it. The Rambam is mashma that the wall was outside the 500 amos, thereby rendering the wall as chol. The Mishkenos Le’Abir Yaakov writes that initially that was the opinion of the Maharil Diskin to be mattir. Another proof that the wall was out of the 500 amos is from the Meiri in Middos Ch 2 where he says the wall was around the Har Habayis where it was flat and the measurement where the mountain starts to slope upwards was 500 x 500 amos.
From all of the above it would seem that there would be no problem touching the Kosel or the cracks between the stones on the wall.
However, the sefer Har Hakodesh pg. 222 writes that the length of Har Habayis from East to West on the North side is 324 meters and on the South side it is 283 meters, as the walls running along the North and South are not even. According to Reb Chaim Naeh the amount of 500 amos translates to 240 meters so one of the two walls was definitely out of the 500 amos. This would be consistent with the Meiri mentioned earlier. On the other hand, if you go with the Chazon Ish’s measurements, 500 amos would translate to between 299 and 300 meters. That would result that a part of each wall is within the 500 x 500 amos. Therefore, it would be consistent with his shitta that one should not touch the wall since part of the wall is built within the 500 amos of Har Habayis.
There is another reason to be meikil because even if we hold that biah be’miktzas is called a biah, and therefore even a partial entering in the Bais Hamikdosh makes one chayav, that is only if had he tried, he could have gone in totally; just because he chose to only enter partially does not exempt him for the biah. In our case, where it is physically impossible to enter in the cracks of the stone with one’s whole body, one would be exempt on such a biah be’miktzas.
We need to understand and show hakoras HaTov to Hashem as the Kosel Hamaravi is the only spot in the world where the Shechina has never moved from. It is the highest point of hashroas Shechina which has never lost its kedusha. This is the reason the place is mesugal for tefillos, and a strong reason we should refrain from touching the wall as to be makeer that this is the only spot in the world where the level of hashroas Shechina, which was so great, never budged. Additionally, the mitzvah of aliya beregel still applies to the Kosel. How lucky are those who visit and treat that holy place with the proper respect!
May we all be zocheh to once again enter the Bais Hamikdash Bikedusha uvetahara!