So it was alway: the cloud covered it by day, and the appearance of fire by night.

Matthew Henry's Concise Commentary

9:15-23 This cloud was appointed to be the visible sign and symbol of God's presence with Israel. Thus we are taught to see God always near us, both night and day. As long as the cloud rested on the tabernacle, so long they continued in the same place. There is no time lost, while we are waiting God's time. When the cloud was taken up, they removed, however comfortably they were encamped. We are kept at uncertainty concerning the time of our putting off the earthly house of this tabernacle, that we may be always ready to remove at the command of the Lord. It is very safe and pleasant going when we see God before us, and resting where he appoints us to rest. The leading of this cloud is spoken of as signifying the guidance of the blessed Spirit. We are not now to expect such tokens of the Divine presence and guidance; but the promise is sure to all God's spiritual Israel, that he will guide them by his counsel. Ps 73:24, even unto death, Ps 48:14. All the children of God shall be led by the Spirit of God, Ro 8:14. He will direct the paths of those who in all their ways acknowledge him, Pr 3:6. At the commandment of the Lord, our hearts should always move and rest, saying, Father, thy will be done; dispose of me and mine as thou pleasest. What thou wilt, and where thou wilt; only let me be thine, and always in the way of my duty. In applying general precepts to particular circumstances, there should be good counsel and fervent prayer. When any undertaking is evidently wrong, or doubtfully right, and yet the mind leans that way, in such a case the moving of the cloud, as men sometimes miscall it, is generally no more than a temptation Satan is permitted to propose; and men fancy they are following the Lord, when they are following their own wayward inclinations. The record of his mercy will conduct us with unerring truth, through Christ, to everlasting peace. Follow the pillar of the cloud and of fire. Lay the BIBLE to heart, and receive with meekness the ingrafted word, which is able to save your souls.