For instance, consider the substance of copper. Were it to be protected in its own mine from becoming solidified, it would, within the space of seventy years, attain to the state of gold.
(Bahá’u’lláh, The Kitáb-i-Iqan, p. 157)
The copper of scorn and derision will be transmuted into the gold of honor and praise.
(‘Abdu’l-Bahá, Bahá’í Scriptures, p. 547)