God told Abraham that before his descendants would inherit the promised land, they would spend 400 years being mistreated in a strange land after which God would judge that nation and bring them out (Gen 15:13-14). Abraham's great-grandson Joseph had 2 dreams about his family bowing to him, although he was the youngest child in a patriarchal family (Gen 37). His brothers were already jealous of him being the favorite. Now they plotted against him. He ended up a slave in Egypt. It did not look like Joseph's dreams would come to pass, but the Lord was with him through everything. When he interpreted the Pharaoh's dreams, he was elevated to second in command under Pharaoh, and when his brothers came to buy food in Egypt during a famine, his dreams were fulfilled (Gen 39-45). Joseph showed profound forgiveness based on his understanding that God had arranged everything that happened to him to position him to save his family and many others from the famine. His family moved to Egypt during the famine (Gen 46), and later the word of the Lord to Abraham was fulfilled (Ex 1).
God called Moses to be the one who led Israel out of bondage in Egypt to the promised land. When he was 40 years old, he went out from the palace of Pharaoh to visit his people (Ex 2). He saw an Egyptian beating an Israelite, and he killed him. When Stephen was recounting the history of Israel before the Jewish council before they killed him, he made an interesting comment about this incident (Acts 7:23-29). Stephen said Moses thought the Israelites would understand that God would use him to deliver them from Egypt (vs 25), and that killing the Egyptian would be a sign to them of that. Instead, he was called into question by his own people and had to flee from Pharaoh for his life. He spent the next 40 years in the desert tending sheep before he could return to do the task God had called him to do (Ex 3-4).
Sometimes God gives us a dream or a vision, or He puts something in our hearts that He wants to do with or through us. God does not usually spell out every detail of how or when it will come to pass. After some time passes, we tend to wonder why it is not happening yet. Even Abraham, the man of faith, did this. That is what led to the Lord telling him about the Egyptian bondage in the first place (Gen 15:1-4). Abraham had been waiting 24 years for this promise when God came to him to tell him it was about to happen (Gen 17). He was still struggling like most of us do (vs 17). He had already attempted to "help" God fulfill His promise 13 years earlier by having a child with his handmaid because his wife was still barren (Gen 16). In Genesis 17, Abraham asked God to accept his attempt to fulfill the promise (vs 18). Yet God did not fulfill the promise Abraham's way, but His way. Sarah did indeed have a son like God promised.
Abraham and Moses tired to "help" God fulfill His promises. Abraham gave birth to Ishmael who became the father of Israel's enemies in the Middle East for millennia (Gen 16:12). Moses committed murder and spent 40 years in the desert. Joseph spent years in slavery and even in prison unjustly until the promise came, but he did not attempt to "jump start" the process by taking matters into his own hands. We need to trust that God's timing, His way, and His control are better than ours. Then He will be glorified for that which only He can do, and we can enjoy the fullness of the blessing He intended for us, even if the road there has difficulties. Don't kill the Egyptian.