Besides being a religious symbol, salt is a universal symbol of alliance and friendship. In cultures all around the world going back for centuries in time it is well attested that when one shares salt with another a bond of friendship is established that requires each to protect and come to the aid of the other in time of need. This was so recognized in many cultures that people often tricked others into eating salt with them so that an alliance would be established. Even if done through trickery, a salt alliance was upheld.
This tradition is part of the New Testament, but it has been lost in translation. For example, the book of Acts begins with Luke explaining to Theophilus that Jesus taught the people for forty days after his resurrection. Then Luke says, “And, being assembled together with them, commanded them that they should not depart from Jerusalem” (Acts1:4). In the original Greek the phrase that is translated as “being assembled together with them” is literally “to take salt in common.” This would have meant something important to Theophilus.
The apostles often “ate salt together.” The very night of Jesus’ betrayal, Judas shared salt with the Savior, and that is why in the beautiful painting of the Last Supper by Da Vinci, if you look closely, you see that Judas holds a bag, presumably the silver, in his right hand, and his left hand has just tipped over a bowl of salt—depicting the fact that Judas had broken the fellowship and the covenant of friendship. He was a traitor.