What was Israel's responsibility concerning the covenant at Sinai?

At Sinai, Israel’s responsibility was conditional: if they would obey God’s voice indeed and keep His covenant. God left them with free will even under His sovereignty, and faith and obedience become almost synonymous. They were to be aware of the covenant and obedient in preparing for its fulfillment.

Les explains that Exodus 19:5 hinges on the conditional word “if.” God says, in effect, “It’s up to you,” so Israel is left with a free will even though they are under a sovereign God. If they will obey His voice and keep His covenant, that is the condition. Les notes that faith and obedience become almost synonymous. God is always bringing up these covenants; though there is more than one, they all boil down to the one master covenant made with Abraham, repeated to Isaac and Jacob—that Israel would become a great nation, dwell in their own land, and one day God would be their king and government. Israel was to be aware of this covenant and obedient in preparing for its fulfillment and being used by God as originally intended. Les also reminds that God deals with the Jew on two levels: national and personal.

Exodus 19:5

Now therefore, if ye will obey my voice indeed, and keep my covenant, then ye shall be a peculiar treasure unto me above all people: for all the earth is mine:

What was Israel's responsibility regarding God's covenant?

Israel's responsibility was to obey God's voice and keep His covenant, as stated conditionally in Exodus 19:5. Their obedience was the condition set before them, and faith and obedience were virtually synonymous. Though under a sovereign God, Israel retained free will and was to prepare for the covenant's fulfillment.