Sefirat ha-omer, lit. the counting of the measure.
Two verses found with the phrase "seven weeks":
Deuteronomy 16:9 Seven weeks shalt thou number unto thee: begin to number the seven weeks from such time as thou beginnest to put the sickle to the corn.
Daniel 9:25 Know therefore and understand, that from the going forth of the commandment to restore and to build Jerusalem unto the Messiah the Prince shall be seven weeks, and threescore and two weeks: the street shall be built again, and the wall, even in troublous times.
Interesting how the hammer and sickle is the same crescent shape throughout history, is the crescent in which the the U.N. logo resides and is on the flags of Muslim and Communists nations throughout the world. Sickle indeed!