God is not a God of sadness, death, etc., but the devil is. Christ is a God of joy, and so the Scriptures often say that we should rejoice ... A Christian should and must be a cheerful person.
Martin LutherNow if I believe in God's Son and remember that He became man, all creatures will appear a hundred times more beautiful to me than before. Then I will properly appreciate the sun, the moon, the stars, trees, apples, as I reflect that he is Lord over all things. ...God writes the Gospel, not in the Bible alone, but also on trees, and in the flowers and clouds and stars.
Martin LutherBut what will happen even if we do burn down the Jews synagogues and forbid them publicly to praise God, to pray, to teach, to utter God's name? They will still keep doing it in secret. If we know that they are doing this in secret, it is the same as if they were doing it publicly. for our knowledge of their secret doings and our toleration of them implies that they are not secret after all and thus our conscience is encumbered with it before God.
Martin Luther