Charity was the "prince among goodly deeds." What is then the "prince of all goodly deeds?"

They that have forsaken their country for the purpose of teaching Our Cause - these shall the Faithful Spirit strengthen through its power. A company of Our chosen angels shall go forth with them, as bidden by Him Who is the Almighty, the All-Wise. How great the blessedness that awaiteth him that hath attained the honor of serving the Almighty! By My life! No act, however great, can compare with it, except such deeds as have been ordained by God, the All-Powerful, the Most Mighty. Such a service is, indeed, the prince of all goodly deeds, and the ornament of every goodly act. Thus hath it been ordained by Him Who is the Sovereign Revealer, the Ancient of Days.

Baha'u'llah, Gleanings from the Writings of Baha'u'llah, p. 334