Mischna zu Tehillim 1:7

Rabbi Hanina, the vice-high priest said: pray for the welfare of the government, for were it not for the fear it inspires, every man would swallow his neighbor alive. R. Hananiah ben Teradion said: if two sit together and there are no words of Torah [spoken] between them, then this is a session of scorners, as it is said: “nor sat he in the seat of the scornful…[rather, the teaching of the Lord is his delight]” (Psalms 1:1); but if two sit together and there are words of Torah [spoken] between them, then the Shekhinah abides among them, as it is said: “then they that feared the Lord spoke one with another; and the Lord hearkened and heard, and a book of remembrance was written before Him, for them that feared the Lord and that thought upon His name” (Malachi 3:16). Now I have no [scriptural proof for the presence of the Shekhinah] except [among] two, how [do we know] that even one who sits and studies Torah the Holy One, blessed be He, fixes his reward? As it is said: “though he sit alone and [meditate] in stillness, yet he takes [a reward] unto himself” (Lamentations 3:28).