Psalm 67 consists of 7 verses ('weeks') and 49 (7x7) Hebrew words (‘days’).

Ps. 67: 1 יהוה be merciful to us, and bless us; and cause his face to shine upon us. Selah. 2 That men may know thy way on the earth, thy salvation among all nations.

Shavuot comes to us from the history of the mountain in Shemot/Exodus 19-24.