This carol was traditionally sung on `Gaudete Sunday', the third Sunday in Advent. There are several interpretations available on the Internet including those by Steeleye Span  by the Oxford Camerata and by Libera with a boys' choir as well as one by dwsChorale in which the words are hear particualrly clearly and which can be heard on the Wikipedia page for the song.  The carol was included in the 16th century Finnish/Swedish collection, Piae Cantiones, but may have originated in Bohemia in central Europe. For more details, see the Wikipedia article and also Gaudium mundo, which explains  the reference in the third stanza  to the gate mentioned in the Old Testament (Ezechiel 44). This was closed after the God of Israel passed through it and would be opened again only for the Prince.  The Latin is translated below word-for-word.

Tempus adest gratiae,                                                    Time is-here of-grace
hoc quod optabamus;                                                     this which we-were-wishing-for
carmina laetitiae                                                                 songs of-joy
devote reddamus.                                                              devoutly let-us-return
CHORUS
Gaudete! gaudete!                                                               Rejoice! rejoice!
Christus est natus ex Maria virgine,                    Christ is born of Mary virgin
gaudete!                                                                                      rejoice!

Deus homo factus est,                                                    God man made has-been
natura mirante;                                                                   with-nature in-astonishment
mundus renovatus est                                                    the-world renewed has-been
a Christo regnante.                                                            by Christ reigning
CHORUS

Ezechielis porta                                                                    Ezechiel's gate
clausa pertransitur;                                                          that-was-closed is-passed-through
unde lux est orta,                                                                from-where light has arisen
salus invenitur.                                                                    salvation is-found
CHORUS

Ergo nostra contio                                                             Therefore our gathering
psallat iam in lustro,                                                        let-it-sing now in offering
benedicat Domino:                                                            let-it-bless the Lord:
salus Regi nostro.                                                               greeting to our King                              
CHORUS