Continuity mistake: When Moses leads the Hebrews from Egypt, he pauses before them to deliver a little speech before they head out into the desert. He faces the camera and lifts his staff up with his left hand. But on the cutaway shot from behind, he is holding the staff in his right hand.
Revealing mistake: When Moses takes the first journey up Mt. Sinai for his very first view of the burning bush, the walking scene shot has Charlton Heston following the camera as the camera dollys backwards towards the bush. As Heston and the camera movement comes to a halt, two long tire tracks in the sand created by the dolly truck that housed the camera and cameraman can be seen.
Continuity mistake: After Rameses slaps the coin out of Dathan's hand, the shot cuts to Dathan being much closer to Rameses. Another instant cut and Dathan is further from Rameses again.
Continuity mistake: When Rameses is asked by Moses if there is any extra grain to feed the slaves, Rameses' pose changes between shots.
Continuity mistake: When Moses and Joshua are reunited and Moses denies God's purpose for him (he says "I am not the man"), Moses has his arm around Joshua's back. In the next shot, Moses is only touching Joshua on the shoulder.
Continuity mistake: When Sephorah first talks to Moses, she is touching the rope holding the bucket over the well. She's not touching it anymore in the next shot.
Continuity mistake: When Moses is exposed as a Hebrew, Sethi is holding his scepter up in his left arm, and Nefretiri tosses her feather to the ground. In the next shot, Sethi's scepter has vanished.
Continuity mistake: When Seti orders that The Deliverer be summoned, he hands the bottle that Rameses gave him earlier without looking at him. In the next shot, he is looking at Rameses.
Continuity mistake: When Seti is told by Rameses that he has caught The Deliverer, Seti is looking at Rameses. In the next shot, Seti is looking straight ahead.
Continuity mistake: When Nefretiri is told by Memnet that there will be a Hebrew on the Egyptian throne, she lowers the cloth that she is holding. In the next shot, she is holding it up higher again.
Answer: I have always thought she stabbed her dead son. It's obvious she does something with it other than just give it to Rameses.
She doesn't do anything other than give him the sword. She's trying to dramatically convince Ramses to kill Moses. In countless stories, one character will tell another character to kill someone while handing them a weapon.