Rare as is true love, true friendship is rarer. Jean de La Fontaine
Everyone calls himself a friend, but only a fool relies on it; nothing is commoner than the name, nothing rarer than the thing. Jean de La Fontaine
Love is rarer than genius itself. And friendship is rarer than love. Charles Péguy
Aristocrats need not be rich, but they must be free, and in the modern world freedom grows rarer the more we prate about it. Robertson Davies
The more necessary a thing is for living beings, the more easily it is found and the cheaper it is; the less necessary it is, the rarer and dearer it is. Maimonides
Beautiful discourse is rarer than emerald, yet it can be found among the servant girls at the grindstones. Egyptian Proverb