"In the midst of a discourse, speak not." ~~ Apocrypha: Ben Sira
"My son, answer not before you hear, nor speak in the midst of converse!" ~~ Ben Sira 11:8
"The test of good manners: to bear patiently with bad ones." ~~ Ibn Gabirol
"Who welcomes his friend with a smile is as one giving him the finest gifts in the world." ~~ Avot Derabbi Nathan
"The junior may not sit down until the senior says: Be seated!" ~~ Talmud Yerushalmi, Ketubot
"Too honor an old man one should not sit in his place or contradict his words." ~~ Rashi
"Be not boastful in your speech! " ~~ Ben Sira 4:32
"There is no truer index to intelligence than the way one acts at the table." ~~ Ibn Gabirol
"Insulting one’s senior is not the same as insulting one’s junior." ~~ Talmud, Ketubot
"Good manners may in Seven Words be found: Forget Yourself and think of Those Around." ~~ Arthur Guiterman
"Talk not while you eat, lest windpipe anticipate gullet (and life be in danger)!" ~~ Talmud, Ta’anit
"Manners provide the lubrication without which frictions would develop." ~~ Rabbi Edgar Magnin