The eating of the fruit of young trees by their owners for five years is forbidden, on the principle that such fruit is unclean until it has been sanctified by the offering of a crop as firstfruits to the Lord for the use of the servants of the tabernacle, and a full crop is not to be expected until the fourth year from the time that the trees were planted.
The fruit is at first to be counted as uncircumcised, being regarded in a position similar to that of the heathen, that is, unclean, from not having been yet sanctified by the offering of the firstfruits.
This sanctification takes place in the fourth year.