פּירוש אויף דברים 5:1

Moshe called out to all Israel to announce the terms of the covenant to the children (as I have explained).

ויקרא משה, Moses called, etc. It is conceivable that as a result of the conquest of the lands of Sichon and Og the Israelites were scattered over a large area at that time. This made it necessary for Moses to call them together. Alternatively, up until this point Moses had addressed only the men; now that he wanted to review the Ten Commandments he made sure that everybody would be present. At the original revelation the entire nation including children had also been present.

ויקרא משה אל כל ישראל, “Moses called all of Israel;” this refers to the children i.e. the generation which had not heard the Ten Commandments first-hand at Mount Sinai. This is why in verse three Moses makes the point that the covenant made between G’d and the people at the time did not only include the generation which was an eye-witness to the revelation but that it included all the subsequent generations of Jews throughout the ages.