Any one can give an invitation, however, this one comes from the only begotten Son of God. Matthew has emphasized this point over and over again, that being, that Jesus of Nazareth is the Messiah, the Son of God. Only God could make such statements, as he makes, and Matthew is clear that Jesus has backed up those claims with divine power. Therefore, the invitation that is extended in these passages is not an idle one, but rather, one coming from the divine Son himself for all men every where. The labor and the rest spoken of here refer to the heavy weight that one shoulders due to sin.
Sin is a spiritual burden.
When a person is laden or burdened and weary with sin, there is only one to whom he may go to receive true and lasting help, and that is Christ. We must turn to him, because he, and he alone, has the answer to the problem of sin. Also, keep in mind that when we turn to Christ out of an obedient faith that our physical lives are changed for the better, as we continue to live the Christian life. The yoke refers back to the use of oxen and their heavy labor. In biblical literature the yoke came to mean a variety of things.