earth - rather, to suit the parallelism, “is a country (put for the people in it) brought forth in one day?” [Lowth]. In English Version it means, The earth brings forth its productions gradually, not in one day (Mar 4:28).
at once - In this case, contrary to the usual growth of the nations by degrees, Israel starts into maturity at once.
for - rather, “is a nation born at once, that Zion has, so soon as she travailed, brought forth?” [Maurer].