This encouraging command has been used in many generations of Sunday school teachings and sermons to challenge the saints. The apostle Paul uses nearly half of the 74 appearances of the word in the New Testament in his epistles.
This simple statement in Philippians 4:4 seems to summarize all of the other passages: "Rejoice |imperative command|--in the Lord |the qualifier, or the 'way' to rejoice|--always |in every circumstance and condition|." Joy is a godly thing.
Because of our sinful condition, we cannot easily "rejoice in the Lord." We can have fleeting moments of happiness and experiences that fill our hearts with delight and pleasure, but true joy--the ability to "rejoice"--only comes "in the Lord."
A quick review from the "Songs" of Israel can help us grasp how the righteous rejoice:
• "Be glad in the LORD, and rejoice, ye righteous: and
shout for joy, all ye that are upright in heart." (Psalm
32:11)
• "Rejoice in the LORD, O ye righteous: for praise is comely
for the upright." (Psalm
33:1)
• "Let all those that seek thee rejoice and be glad in thee:
let such as love thy salvation say continually, The Lord be
magnified." (Psalm
40:16)
• "My lips shall greatly rejoice when I sing unto thee; and
my soul, which thou hast redeemed." (Psalm
71:23)
• "Rejoice in the LORD, ye righteous; and give thanks at the
remembrance of his holiness." (Psalm
97:12)
Joy and rejoicing from born-again believers produce emotion (gladness, cheering, praise, singing, thanks, etc.), but the object of the emotion is always the source of our joy--the Lord Jesus our Savior, King, and Creator. HMM III