Midrash su Isaia 33:18

Samuel found R. Juda standing leaning against the entrance of a door and weeping. He said to him: "Keen scholar, why weepest thou?" He replied: "Is it a small matter that is written concerning the Rabbis (Is. 33, 18) Where is He who wrote down? Where is He that weighed? where is he that counted the towers? "Where is he that counted?" this means scholars who counted all the letters that are in the Books of the Law. Where is he that weighed? Referring to those who weighed the light and the heavy things which are in the Law. Where is he that counted the towers? Referring to those who taught three hundred doctrines concerning the law of a tower which flies in the air." And R. Ami said: "Three hundred questions were treated by Doeg and Ahithophel concerning the law of a tower which flies in the air." And we are taught, however, in a Mishnah: "Three kings and four private persons have no share in the world to come, and we — what will there be for us?" Samuel said: "Keen scholar there it was because they bore impurity in their hearts (i.e., heathen sensuality)."

(Ib. b) R. Isaac said again: "What is the meaning of the passage (Isa. 33, 18) Where is he who wrote down; where is he that weighed; where is he that counted the towers? i.e., where is he who counted the letters of the Torah? Where is he who weighs the lenient and rigorous things mentioned therein? Where is he who counted three hundred decided Halachas [about Levitical cleanliness] concerning a turret flying in the air?" R. Ami said: "Four hundred questions had Doeg and Achitophel raised concerning turrets flying in the air, and not one of them could be decided." "Is it then a great thing to ask questions?" remarked Raba. "In the years of R. Juda all their studies were confined to the Section of Damages, etc. We must therefore say that the Holy One, praised be He! desires a [pure] heart of one [but not his mouth], as it is written (I Sam. 16, 7) But the Lord looketh on the heart."