What was the shamir, and why was it used in building the Temple?
The shamir is one of the things created at sundown on the sixth day of Creation (Mishnah Avos 5:6). The Talmud (Pesachim 59a) tells about its power to cleave stone, but doesn’t describe the process in detail; the commentators (Rashi on Pesachim, Rambam on Avos) explain that it was a worm that could cleave stone by looking at it. Solomon used it to build the Temple because using metal implements was forbidden (Ex. 20:22; Deut. 27:5); see Tosefta Sotah 15:1 and Talmud Sotah 48b. For more details about the shamir see Ginsburg, Legends of the Jews, Vol.1 pp.33-4; Vol.4 pp.166,168; Vol.5 pp.53,109; Vol.6 pp.282,299.
All the Best,
Rabbi Azriel Schreiber
