יקום הבן על שם אחיו, he will arise in the name of his brother (deceased). This is the plain meaning.

וחלצה נעלו, in order thereby to acquire the inheritance of his deceased brother, as we know from the situation of Boaz (Ruth 4,7-8) [according to the view of Levi in Baba Metzia 47 that chattels of the party transferring the property, מקנה, are used for that purpose. This is not the halachically accepted view. Ed.]

גדולה וקטנה, the vendor make himself two weights each marked as representing the same measure, but one being smaller than the other. When using both simultaneously, i.e. filling each next to the other, the total quantity is correct, but one represents more than half, the other less. It is therefore easy to deceive a customer who has once observed that when the two are used together they give the correct measure. This is why the Torah demands that “each” measure must be true in quantity of weight, i.e. אבן שלמה, “a true weight, etc.,” instead of “true weights.”

שלמה וצדק, one single chunk, (not composites) true and fair.

אשר קרך בדרך, meaning “accidentally,” unforeseen. The construction קרך from the root קרה is parallel to the construction עשך from the root עשה, Deut. 32,6 הוא עשך ויכוננך, “He has shaped you and made you durable.”