Jerome.
"Letter XXII. To Eustochium." (read paragraphs 7 & 12) from Jerome.
Select Works and Letters. The Nicene and Post-Nicene Fathers
Series II. vol. 6. The
Early Church Fathers
Saint Jerome: Doctor of Biblical Studies by Brother Francis, M.I.C.M. from Catholicism.Org
An excerpt of Jerome's Letter 22 to Eustachuim in Latin (to find the excerpt, click on the link & search for beatitudo) from Prof. Blasius Amata