Contradiction with Proverbs 13:23
While Isaiah 17:5 speaks of harvesting, Proverbs 13:23 suggests abundance even where there is not much reaping.
Proverbs 13:23: Much food [is in] the tillage of the poor: but there is [that is] destroyed for want of judgment.
Contradiction with Matthew 13:30
Isaiah 17:5 assumes a complete harvest, whereas Matthew 13:30 allows the tares to grow until the harvest.
Matthew 13:30: Let both grow together until the harvest: and in the time of harvest I will say to the reapers, Gather ye together first the tares, and bind them in bundles to burn them: but gather the wheat into my barn.
Contradiction with John 4:35
Isaiah 17:5 talks of imminent action, while John 4:35 mentions waiting for the right season.
John 4:35: Say not ye, There are yet four months, and [then] cometh harvest? behold, I say unto you, Lift up your eyes, and look on the fields; for they are white already to harvest.
Contradiction with 1 Corinthians 3:6
Isaiah 17:5 illustrates human action in harvest, whereas 1 Corinthians 3:6 emphasizes that God gives the increase.
1 Corinthians 3:6: I have planted, Apollos watered; but God gave the increase.
Contradiction with Ecclesiastes 11:4
Isaiah 17:5 describes a straightforward harvest, while Ecclesiastes 11:4 warns against being hindered by weather in sowing and reaping.
Ecclesiastes 11:4: He that observeth the wind shall not sow; and he that regardeth the clouds shall not reap.