A song of ascents. 

Psalms 120-134 are called “the psalms of ascents.” A better name would be “the songs of the pilgrim caravans.” These pilgrimage songs were sung when Israel traveled upwards to Jerusalem (usually in caravans) during the Jewish feasts of Passover, Pentecost, and Tabernacles. Four of these songs were attributed to David. Solomon wrote one of these songs. The other ten songs are anonymous. The author of Psalm 134 is unknown.

134:1 Attention! Praise the Lord, all you servants of the Lord, who serve in the Lord’s temple during the night. 

The Hebrew word for “attention” is הִנֵּ֤ה (hinah), meaning to pay close attention, because an important Bible doctrine is about to be discussed. All of the Levitical priests were commanded to praise Jehovah.

134:2 Lift your hands toward the sanctuary and praise the Lord!

The Jews were to lift their hands towards the temple and praise Jehovah.

134:3 May the Lord, the Creator of heaven and earth, bless you from Zion!  

Jehovah is the Creator of heaven and earth. He will bless those who praise Him. He will bless them from Jerusalem. This blessing will occur in the Millennial Kingdom when the Lord Jesus Christ rules from Jerusalem.