Commentary for Exodus 23:19

ראשית בכורי אדמתך THE FIRST OF THE FIRST-FRUITS OF THY GROUND [THOU SHALT BRING etc.] — Even in the seventh year the offering of the first fruits is obligatory in some cases, therefore here also (where Scripture mainly deals with the laws of the Sabbatical year) it is stated: “the first of the first-fruits of thy land [shalt thou bring, etc.]”. How was the procedure at the setting apart of the first fruits? A man goes into his field and sees a fig which was the first to ripen; he ties a piece of reed-grass round it to distinguish it and so marks its sacred character (Mishnah Bikkurim 3:1). The law of the first fruits applies only to the seven kinds of produce that are mentioned in Scripture: (Deuteronomy 8:8) “a land of wheat and barley etc.”, for which Palestine is praised in that verse (Mishnah Bikkurim 3:1).

ראשית בכורי אדמתך, "The choicest first-fruits of your soil, etc." Perhaps the Torah hints here that one must not destroy one's seed (semen) and that the son born of one's first seminal emission should be dedicated to the service of the Lord (compare Yuma 2 according to which the word ביתו is an oblique reference to one's wife)

ראשית בכורי אדמתך, this includes the seven types of products (Deut. 8,8) considered as the land of Israel’s choicest as per Deuteronomy 26,2 where you are commanded to bring the respective first ripe specimen of these seven products to Jerusalem as a gift. Ascent to Jerusalem with these products is to be on foot.