"Engrave on it with signet-ring [type] engraving: "Holy to Hashem"   פִּתּוּחֵי חֹתָם קֹדֶשׁ לַי־הֹוָ־ה  [Tetzaveh 28:36] In Maseches Ta'anis (2a) R' Yochanan states that there are three maftechos, three keys, in Hashem's possession that He never entrusts to others: the Key to childbirth the key to rain and the key to resuscitating the dead The Gemara derived this from three