David’s men had been protecting Nabel’s sheep and shepherds. As compensation for this he asked Nabal to send whatever he thought fair.

Source: 1^st Samuel 25:4-9

He called him to interpret the writing on the wall.

Source: Daniel 5

Who will gather the last harvest in Revelation?

The Son of Man(Jesus) will gather the last harvest. An Angel will help him.

Source: Revelation 14:14-19

Part of the harvest was to leave provision for the poor and the stranger. What did God command the nation of Israel to do?

They were not to harvest the entire field but to leave the corners for the poor and travelers. Also they were not to glean the fields for the same reason.

Source: Leviticus 23:22

In the gospel Jesus said the harvest is great but one thing was lacking for gathering it. What was missing?

Laborers are needed to gather the harvest.

Source: Matthew 9:37, Luke 10:2

In the Old Testament could Jews work on the Sabbath during harvest?

They could not the Sabbath was protected even during Harvest.

Source: Exodus 34:21