Psalm 23 NIV

A psalm of David.
1 The LORD is my shepherd, I lack nothing. 2 He makes me lie down in green pastures, he leads me beside quiet waters, 3 he refreshes my soul. He guides me along the right paths for his name’s sake. 4 Even though I walk through the darkest valley,I will fear no evil, for you are with me; your rod and your staff, they comfort me. 5 You prepare a table before me in the presence of my enemies. You anoint my head with oil; my cup overflows. 6 Surely your goodness and love will follow me all the days of my life, and I will dwell in the house of the LORD forever.

One of the best known Psalms is psalm 23 which is sung at both funerals and weddings, I suppose the reason for it being sung at weddings is the words from verses 3 and 4 where we ask for guidance and in dark times as for comfort from you from the evil one.