1 After the promise of the Holy Spirit, lest any should suppose that the Lord was to give Him, as it were, in place of Himself, in any such way as that He Himself would not likewise be with them, He added the words: “I will not leave you orphans; I will come to you.” Orphani [Greek] are pupilli [parent-less children] in Latin. The one is the Greek, the other the Latin name of the same thing: for in the psalm where we read, “You are the helper of the fatherless” [in the Latin version, pupillo], the Greek has orphano . Accordingly, although it was not the Son of God that adopted sons to His Father, or willed that we should have by grace that same Father, who is His Father by nature, yet in a sense it is paternal feelings toward us that He Himself displays, when He declares, “I will not leave you orphans; I will come to you.” In the same way He calls us also the children of the bridegroom, when He says, “The time will come, when the bridegroom shall be taken away from them, and then shall the children of the bridegroom fast.” And who is the bridegroom, but Christ the Lord?
Source: Tractates on the Gospel of John (New Advent)