Jesus was referring, not to a literal harvest, but to a spiritual ingathering of righthearted individuals who would become his followers.
وَفِي ٱلْوَاقِعِ ،‏ كَانَتْ كَلِمَاتُهُ هذِهِ دَعْوَةً إِلَى ٱلْعَمَلِ .‏