Well, if you think about the posture–hands pointed outward toward heaven–it appears symbolic of reaching toward God. It is a posture of entreaty and appealing for help. It’s not that different from children reaching for their parents.
Ezra 9:5, “But at the evening offering I arose from my humiliation, even with my garment and my robe torn, and I fell on my knees and stretched out my hands to the LORD my God.”
We see this sense of asking for help in the Psalms. Psalm 28:2, “Hear the voice of my supplications when I cry to You for help, When I lift up my hands toward Your holy sanctuary.”
Also, Lamentations 3:41 where the act of lifting the hand is associated with lifting the heart, “We lift up our heart and hands Toward God in heaven.”
It is likened to an offering to God: Psalm 141:2, “May my prayer be counted as incense before You; The lifting up of my hands as the evening offering.”
In another sense, it signifies blessing. When we lift our hands, we are blessing the Lord. Psalm 134:2, “Lift up your hands to the sanctuary And bless the LORD.”