Another interpretation (of Proverbs 14:23): "In all toil there is profit." This speaks of toil over Torah. One who toils over it more than his fellow in Torah shall have advantage, and he has gain. (The same verse continues:) "but the talk of lips leads only to want." Whatever a person withholds his lips from — so that he does not labor in Torah — leads only to want. It once happened that there was a certain student who was diligent, and Rabbi Eleazar ben Jacob was his name. He was constant in his study. See how constant he was in his study: even while he was sweating in the bathhouse, he would stand in his place and go over his study. Because he was not voicing it with his lips, he fell ill and forgot his study. What caused this for him? Through his not voicing it with his lips. Therefore it is said, "but the talk of lips leads only to want."
Why Rabbi Eleazar ben Jacob Forgot His Silent Torah Study
Midrash Tanchuma Buber, Miketz 2:2
ד"א בכל עצב יהיה מותר מן חבירו בתורה יהא מותר ויתרון יש לו, ודבר שפתים אך למחסור (שם) מה שהוא חושך את שפתיו שלא יגע בתורה אך למחסור. מעשה בתלמיד אחד שהיה וותיק, ור' אלעזר בן יעקב שמו היה רגיל בתלמודו, ראה מה היה רגיל בתלמודו, עד שהוא מזיע במרחץ היה עומד על עמדו ועובר על תלמודו, בשביל שלא היה יודע בשפתיו חלה ושכח תלמודו, מי גרם לו על ידי שלא היה יודע בשפתיו, לכך נאמר ודבר שפתים אך למחסור.