The Literal Commandment
The literal commandment: "You shall not sow your vineyard with two kinds of seed, or all the produce of the seed which you have sown and the increase of the vineyard will become defiled." (Deuteronomy 22:9)
The literal commandment is that we are not to cow a vineyard with two kinds of seed. If we were to do so, the produce of the seed and the vineyard would become defiled.
Messiah Says
Messiah implicitly affirmed this commandment when He spoke about the Law:
"Do not think that I came to abolish the Law or the Prophets; I did not come to abolish but to fulfill. For truly I say to you, until heaven and earth pass away, not the smallest letter or stroke shall pass from the Law until all is accomplished. Whoever then annuls one of the least of these commandments, and teaches others to do the same, shall be called least in the kingdom of heaven; but whoever keeps and teaches them, he shall be called great in the kingdom of heaven. (Matthew 5:17-19)
Pictures of Messiah
Throughout Scripture, vineyards are used as a picture the nation of Israel (Isaiah 5, Matthew 21, John 15, etc). We repeatedly see G-d's instruction that we are not to mix diverse seeds in the vineyard and Israel is not to mix with the nations whether in their marriages (Deuteronomy 7:3), in their behavior (Deuteronomy 5:31-33), or in their form of worship (Deuteronomy 12:29-30). Paul reiterates such a distinction in 2 Corinthians 6:14 that believers should not be bound together with unbelievers.
Why?
Consider the parable of the wheat and the tares. The landowner (i.e. G-d) sowed the field with a single good seed. The enemy sows tares (weeds) among the wheat and adulterates it.
This commandment pictures Messiah as the perfectly sinless and undefiled field sown with the seeds of believers. While the enemy has sown weeds of unbelievers among the body of Messiah, in the end "The Son of Man will send forth His angels, and they will gather out of His kingdom all stumbling blocks, and all those who do evil, and will throw them into the furnace of fire; in that place there will be weeping and gnashing of teeth." (Matthew 41-42)
How Messiah Fulfilled
We know that Messiah did not sin (Hebrews 4:15) and so we know Messiah fulfilled this commandment by not eating diverse seeds planted in a vineyard.
Traditional Observance
The traditional observance of this commandment is found in its literal meaning: not eating diverse seeds planted in a vineyard.
Other Notes
We are able to fulfill this commandment today and should not eat diverse seeds planted in a vineyard.
Some question whether or not this commandment is applicable outside the Land of Israel given the first portion of the verse, "when you enter the land and plant all kinds of trees for food...".
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