Is it Really a Sin to Grieve on the Sabbath?

While our S3 Clergy Group was on retreat in Idaho, I had an opportunity to read The Sabbath by Abraham Heschel. I have struggled with how to apply Heschel's admonition that it is a sin to be sad on the Sabbath, and that sabbath should not be marred by grief. Quite frankly, this one thought has made it difficult for me to move on and appreciate other insights from Heschel that would be easier for me to embrace. My best friends' 21-year-old son was killed in action in Afghanistan on August 6. As I was standing and singing in a worship service recently with my daughter, grandson, and my son-in-law soldier home from Kuwait for 15 days of R&R, my emotions alternated between rejoicing to have my son-in-law home safe for a few days and weeping for my friends' loss of their son who was killed just a few weeks before he was scheduled to come home for R&R. In Romans 12:15, the Apostle Paul instructs, "Rejoice with those who rejoice, and weep with those who weep." In Colossians 2:16-17, Paul again writes, "let no one act as your judge...in respect to...a Sabbath day - things which are a mere shadow of what is to come; but the substance [or reality] belongs to Christ." Granted, Heschel is making a legitimate point as a general rule; however, it seems that the New Testament helps to remind us that authentic relationship allows us to accept the reality that we do not have to suppress, ignore, or deny our grief even during sabbath, while at the same time rejoicing that we are sons and daughters of the Most High who is with us in the midst of our sorrows.