John Gill

And in the fifth year shall ye eat of the fruit thereof,.... And so in all succeeding years as long as the tree lasted and bore: that it may yield unto you the increase thereof; may be so abundantly blessed, and produce so large an increase as to answer the three years' want of any fruit from it, and the dedication of the fruit of the fourth year to the Lord: I am the Lord your God; who has promised this increase, is both able and faithful to make it good.