This is a terrific song by Bob Hurd in a Latin style with one set of verses for gathering and another for sending forth. Oddly it sounds a bit like the bush ballad “Augathella Station”.
The text of the refrain is here (page 3) and it can purchased for download at OCP if you want the rest of the lyrics. You can hear the whole song at this site.
This parish have a red hot go at the gathering version with almost enough guitars: