Verb
To make strong or stronger; to add strength to; as, to strengthen a limb, a bridge, an army; to strengthen an obligation; to strengthen authority.
To animate; to encourage; to fix in resolution.
To grow strong or stronger.
Source: Webster's dictionaryDifficulties strengthen the mind, as labor does the body. Seneca
Challenges strengthen your soul. Sergei Bodrov Jr.
For there is no friend like a sister In calm or stormy weather; To cheer one on the tedious way, To fetch one if one goes astray, To lift one if one totters down, To strengthen whilst one stands. Christina Rossetti
Lower your voice and strengthen your argument. Lebanese Proverb
Bread and wine strengthen the back. Sicilian Proverb
Every time you forgive a man you weaken him and strengthen yourself. American Proverb