“You shall not sow your vineyard with different kinds of seed, lest the yield of the seed which you have sown and the fruit of your vineyard be defiled.You shall not plow with an ox and a donkey together.You shall not wear a garment of different sorts, such as wool and linen mixed together.”
To properly understand the Law of God, we must keep in mind that it served multiple purposes. Part of the Law was moral and set a standard for all mankind. It is that part of the law Paul referred to as a tutor designed to lead us to Christ (Galatians 3:24). Other portions of the law were civil, and designed to guide the behaviors of the people of Israel that they might have a healthy society. Finally, there were portions of the law that were religious by nature, and their purpose was to guide Israel in their worship of God.
The text before us does not seem to be moral or civil, and therefore, must be seen as a part of the religious aspect of the law. The question is, why would God not allow different seeds, animals, or cloth to be linked together? I suggest that it has less to do with farming and fashion than it does with illustrating a key element in following Christ. Just as two animals would pull differently on the same plow, or two fabrics will shrink at different rates, so too, will believers and unbelievers head in different directions and pull against one another. This is the illustration behind the New Testament principle of not being unequally yoked together with unbelievers (2 Corinthians 6:14). If your desire is to grow in Christ, become like Christ, and faithfully serve Christ, then you want to surround yourself with others who will pull you in that direction. If your primary influences in life are people who do not desire to serve the Lord, you will find it very difficult to be constantly fighting against those influences. That does not mean we should avoid people who are not followers of Christ, but we should have a group of men and women who will constantly encourage us in Christ. Keep in mind, it was Jesus who chose twelve men, pulled them out of the world, and spent three years with them. After His death, they continued to build one another up as they followed the Lord.