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Et sic de similibus references:

The harvest is plenteous and the labourers are few.
Mat 9:37
Then saith he unto his disciples, The harvest truly [is] plenteous, but the labourers [are] few;

The fields are white onto harvest and there are very few willing to go into the fields to reap.
Jhn 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.
Luk 10:2
Therefore said he unto them, The harvest truly [is] great, but the labourers [are] few: pray ye therefore the Lord of the harvest, that he would send forth labourers into his harvest.

Multitudes are standing at the threshold of  the door of salvation and very few labourers are willing to lead those multitudes through the door to everlasting life.
Joe 3:14
Multitudes, multitudes in the valley of decision: for the day of the LORD [is] near in the valley of decision.

Many excuses God's servants give for not labouring in God's vineyard, yet not one of those excuses is valid.
All excuses center on one notion, the lack of Faith.
Faith is the willingness to abandon all one's own ways in favor of God's.
It is simply a case of not putting the Kingdom of God first.
Luk 14:16-21
Then said he unto him, A certain man made a great supper, and bade many:
And sent his servant at supper time to say to them that were bidden, Come; for all things are now ready.
And they all with one [consent] began to make excuse. The first said unto him, I have bought a piece of ground, and I must needs go and see it: I pray thee have me excused.
And another said, I have bought five yoke of oxen, and I go to prove them: I pray thee have me excused.
And another said, I have married a wife, and therefore I cannot come.
So that servant came, and shewed his lord these things. Then the master of the house being angry...
Luk 14:23-24
And the lord said unto the servant, Go out into the highways and hedges, and compel [them] to come in, that my house may be filled.
For I say unto you, That none of those men which were bidden shall taste of my supper.

Come, let us go into all the world and tell those poor souls of the wonderful message of salvation, deliverance and hope wrought by the cross of Christ.
Mar 16:15
And he said unto them, Go ye into all the world, and preach the gospel to every creature.