2 The pilgrim Church is missionary by her very nature, since it is from the mission of the Son and the mission of the Holy Spirit that she draws her origin, in accordance with the decree of God the Father. This decree, however, flows from the "fount - like love" or charity of God the Father who, being the "principle without principle" from whom the Son is begotten and Holy Spirit proceeds through the Son, freely creating us on account of His surpassing and merciful kindness and graciously calling us moreover to share with Him His life and His cry, has generously poured out, and does not cease to pour out still, His divine goodness. Thus He who created all things may at last be "all in all" (1 Cor. 15:28), bringing about at one and the same time His own glory and our happiness. But it pleased God to call men to share His life, not just singly, apart from any mutual bond, but rather to mold them into a people in which His sons, once scattered abroad might be gathered together (cf. John 11:52).
Source: Ad Gentes (Vatican.va)