Why does the Lord say that he did not command the fathers concerning burnt offerings and sacrifices when he brought them out of Egypt, but rather commanded them to obey his voice?

Through his prophet, the Lord is reminding the people that the order of events during the Exodus is critical in understanding the nature of the covenant relationship the Lord has with them. When he brought them out of Egypt during the Exodus, he brought them to Mt Sinai and entered into a covenant with them, not by first giving them the sacrificial system, but by saying to them, You yourselves have seen what I did to the Egyptians and how I bore you on eagle’s wings and brought you to myself. Now therefore, if you will indeed obey my voice and keep my covenant, you shall be my treasured possession among all the peoples, for all the earth is mine, and you shall be for me a kingdom of priests and a holy nation (Exodus 19:4–6. To this the people responded by saying, All that the Lord has spoken we will do (Exodus 19:8). The basis of the Lord’s covenant with Israel was his gracious rescue of them from Egypt and their response of unconditional obedience to his voice. The Lord then gives them the Ten Commandments in Exodus 20:1–17 and only in Exodus 24:1–18 are details of the temple and sacrifices given.¹ Obey me, and I will be your God expresses a key theme in Jeremiah’s theology of the covenant (Jeremiah 11:4; Jeremiah 24:7; Jeremiah 30:22; Jeremiah 31:1; Jeremiah 32:38).² Throughout the book of Deuteronomy, the aspect of the covenant that is emphasized is a wholehearted love for the Lord (Deuteronomy 6:4–5; Deuteronomy 10:12–13). Rescue and obedience to the Lord’s voice came before sacrifices. The Lord did not want their sacrifices if they were not living in obedience to his voice. So, in Jeremiah 7:22–23 the Lord is not rejecting the whole sacrificial system given at Mt Sinai, but he is rather rejecting empty, hypocritical worship from the people of Jeremiah’s day who no longer live in obedience to his voice.