Shavuos 35 - 41
World Shaking Words
When the court administers an oath in a financial case the judges impress upon the party about to take the oath the gravity of swearing falsely. "Be aware," they tell him, "that the entire universe trembled when Hashem said at Sinai: 'You shall not take the Name of Hashem your G-d in vain.'"
The gravity of this sin, points out the Talmud, lies in the fact that the Torah says that Hashem does not absolve the one who swears falsely with His Name. For all other sins repentance alone can achieve Heavenly absolution, but taking Hashem's name in vain must receive some sort of punishment even with repentance.
The trembling of the universe, explains Maharsha, was based on the fact that Hashem created the world by uttering His sacred Name. One who defiles that Name by swearing falsely with it is therefore guilty of shaking the very foundation of existence.
- Shavuos 39a
Hospitality towards guests is greater even than receiving the Divine Presence.
This is deduced from the Torah account of Avraham Avinu welcoming three guests to his home. Although the Divine Presence had come to pay a sick call to him while he was recovering from his Bris Milah, Avraham excused himself with the plea "Hashem if I have found favor in Your eyes please do not leave Your servant" (Bereishis 18:3) in order to attend to his guests.
- Shavuos 35b