On that day, i.e. about that time, for it was not done till some days after their passing over. Day is oft put for time, as hath been noted before. Plaister them with plaister, for conveniency of writing upon them.
Related Commentaries of Deuteronomy 27:2
Deuteronomy 27:2
2 And it shall be on the day when ye shall pass over Jordan unto the land which the LORD thy God giveth thee, that thou shalt set thee up great stones, and plaister them with plaister: