– See Hebrews 1:9, which is a quotation from Psalm 45:7. These verses speak of the joy that comes to those who choose righteousness over lawlessness as a way of life. Righteousness, of course, begins with being yoked to Christ and lawlessness to resistance to Christ’s laws. As for the ease or difficulty of Christ’s yoke, see Matthew 11:28-30. As for His laws, see John 15:17.
– Jesus describes in John 15:10-11 how His joy comes to be present in us when we live for His will instead of our own.
– Isaac Watts wrote the words to his hymn “Joy to the World” based on the words of Psalm 98. His purpose in hymn writing was the translate the ideas of the Psalms into contemporary words for his day which spoke specifically of Jesus Christ as Lord.