'Memorial' in the Bible

Joshua told them, "Cross over again in front of the ark of the LORD your God into the middle of the Jordan River. Then each of you pick up a stone on his shoulder with which to build a memorial, one for each of the tribes of Israel.

Then ye shall answer them, That the waters of Jordan were cut off before the ark of the covenant of the LORD; when it passed over Jordan, the waters of Jordan were cut off: and these stones shall be for a memorial unto the children of Israel for ever.