The variety of inherited qualities comes from strength and
weakness of constitution — that is to say, when the two parents are weak, the
children will be weak; if they are strong, the children will be robust. In the
same way, purity of blood has a great effect; for the pure germ is like the
superior stock which exists in plants and animals. For example, you see that
children born from a weak and feeble father and mother will naturally have a
feeble constitution and weak nerves; they will be afflicted and will have
neither patience, nor endurance, nor resolution, nor perseverance, and will be
hasty; for the children inherit the weakness and debility of their parents.
(‘Abdu’l-Baha,
table talks in Akka, authenticated by ‘Abdu’l-Baha; ‘Some Answered Questions’; The Compilation of Compilations, Vol. I,
Family Life)