Allah, the Exalted, informs that He commanded Musa to journey at night with the Children of Israel, when Fir`awn refused to release them and send them with Musa. He was to take them away from Fir`awn's captivity. Allah expounds upon this in Surahs other than this noble Surah. Musa left with the Children of Israel, and when the people of Egypt awoke in the morning they found that not a single one of them remained in Egypt. Fir`awn became extremely furious. He sent callers into all of the cities to gather together his army from all of his lands and provinces. He said to them,
The decisive defeat which he suffered in the contest between the right and wrong and between miracle and magic broke the power of the Pharaoh, and the Bani Isra'ile stood united under the leadership of Sayyidni Musa (علیہ السلام) . Allah now commanded Sayyidna Musa (علیہ السلام) to take his men out of Egypt. But this move was full of danger. First there was the risk of pursuit by the Pharaoh, and second the river, which they had no means of crossing, barred their flight. Allah dispelled both these fears from Sayyidna Musa (علیہ السلام) mind and told him to strike his staff on the surface of the water, and dry passageways would appear in the bed of the river over which they could all escape, thus frustrating Pharaoh's pursuit. This story has been narrated earlier under Hadith ul-Futun in this very Surah.
After the confrontation with the magicians, Moses remained in Egypt for many years. On the one hand, he persisted with his preachings to Pharaoh and his community, while on the other hand, he demanded that he be allowed to take his people along with him out of Egypt to the Sinai desert, so that they could freely pray to the one and only God. But Pharaoh neither accepted his advice, nor did he allow him to leave Egypt. At last, at God’s behest, Moses decided to migrate in secrecy. In accordance with a predetermined plan, all the Israelite as well as non-Israelite believers who were there in Egypt at that time gathered at a particular place and from there collectively marched onwards. No sooner had this caravan reached the northern Gulf of the Red Sea than Pharaoh arrived there in pursuit of them with his army. Before them was the wide gulf like a vast sea and behind them was Pharaoh’s army. Then, Moses struck the water of the gulf with his stick, and the water divided into two parts. Moses and his companions, walking on the dry land in the middle, reached the other side safely. On seeing this, Pharaoh also embarked on the same course. But as soon as Pharaoh and his army reached the middle, the two separate walls of the water gushed back in and joined together, so that they were all drowned. The same sea, which had provided a path of deliverance to God’s faithful subjects, became a pit of death for His enemies. Generally, people who rely on their leaders ignore the Truth. Pharaoh’s example certainly shows that a leader’s support can be very weak. In this world, those who chalk out their path by following God’s signs rather than the dictates of some great national figure are the ones to enjoy real support.
Uthmani text of the Madinah mushaf (King Fahd Complex). Translation: Saheeh International. Tafsir via Quran.com.