Daily Rambam

Rabbi said: Due to sins of not keeping oaths, one’s children die when they are minors, as the pasuk says: “Do not allow your mouth to cause evil to your flesh … why should Hashem be angry at you over your voice [Rashi- the oath you uttered] and destroy the work of your hands [i.e., your children]? (Kohelet 5:5).

One day the three [candidates for conversion, who were rejected by Shammai and accepted by Hillel] happened to be in the same place. They said: The kapdanut (exacting, intolerant nature) of Shammai attempted to have us lose our place in the world, and the anvatanut (humility, patience, tolerance) of Hillel brought us close under the wings of the Divine Presence.