A sign is a symbol that points to something of more significance. Any object action, event, pattern etc. that conveys a meaning is a sign.
Looking at the account when God told Moses to get the children of Israel out of Egypt, Pharaoh did not set his heart on those signs leading to hardness of heart. If Pharaoh had allowed the children of Israel to go after the first sign, he and his host would not have ended up the way they did. Exodus 4: 8 reads “And it shall come to pass, if they will not believe thee, neither hearken to the voice of the first sign, that they will believe the voice of the latter sign”. In other words, a sign has a voice. Its speaking something.
In the book of Exodus we have the account where Moses went up to mount Sinai twice to receive instructions and the ten commandments from God. He was in the mount for 40 days and 40 nights (Exodus 24; 18) on both occasions (Exodus 34; 28).
The first account can be found from (Exodus 24; 18 to 31; 18) and (Exodus 32 ).
Sacrifice is a step beyond convenience. Bill Johnson