According to the statute, the two trumpets, which were of very simple make, and capable of only a few notes, had their use first in calling assemblies. A long peal blown on one trumpet summoned the princes who were the heads of the thousands of Israel: a long peal on both trumpets called the whole congregation to the "tent of meeting." There were occasions when these assemblies were required not for deliberation, but to hear in detail the instructions and orders of the leader. At other times the convocations were for prayer or thanksgiving; or, again, the people had to hear solemn reproofs and sentences of punishment. We may imagine that with varying sound, joyful or mournful, the trumpets were made to convey some indication of the purpose for which the assembly was called. A sacred obligation lay on the Israelites to obey the summons, whether for joy or sorrow. They heard in the trumpet-blast the very voice of God. And upon us, bound to His service by a more solemn and gracious covenant, rests an obligation even more commanding. The unity of the tribes of Israel, and their fellowship in the obedience and worship of Jehovah, could never be of half so much importance as the unity of Christians in declaring their faith and fulfilling their vocation. To come together at the call of recurring opportunity, that we may confess Christ and hear His word anew, is essential to our spiritual life. Those who hear the call should know its urgency and promptly respond, lest in the midst of the holiest light there come to be a shadow of deep darkness, the midnight gloom of paganism and death. Again, in the wilderness, the trumpets gave the signal for striking the camp and setting out on a new stage of the journey. Blown sharply by way of alarm, the peals conveyed now to one, now to another part of the host the order to advance. The movement of the pillar of cloud, we may assume, could not be seen everywhere, and this was another means of direction, not only of a general kind, but with some detail.