Letter 1, earlier entitled Singuli dies with a date of 24 March 1930, is on the call to holiness and apostolate in ordinary life.
Four main sections can be identified in this Letter:
a) the faithful of Opus Dei are instruments in the hands of God to call all souls to holiness (nos. 1-3).
b) This call to holiness and apostolate is within the context of ordinary life, in the fulfilment of one’s duties in professional life, family life, etc., small things, normally carried out naturally and through effort, without attracting attention, because Christians should act – as Jesus taught us – as yeast within the dough (nos. 4-19).
c) Humility is the foundation of this ascetical task. A humility which, in Opus Dei, is both personal and collective, and leads one to act at every moment with rectitude of intention and naturalness (nos. 20-21).
d) An awareness of the mission received as members of Opus Dei to help draw many people close to Christ, through personal apostolate (nos. 22-23).