Exodus 19:9

9 The Lord said to Moses, "I will come to you in a thick cloud, so that the people will hear me speaking with you and will believe you from now on." Moses told the Lord what the people had answered,

Exodus 19:9 In-Context

7 So Moses went down and called the leaders of the people together and told them everything that the Lord had commanded him.
8 Then all the people answered together, "We will do everything that the Lord has said," and Moses reported this to the Lord.
9 The Lord said to Moses, "I will come to you in a thick cloud, so that the people will hear me speaking with you and will believe you from now on." Moses told the Lord what the people had answered,
10 and the Lord said to him, "Go to the people and tell them to spend today and tomorrow purifying themselves for worship. They must wash their clothes
11 and be ready the day after tomorrow. On that day I will come down on Mount Sinai, where all the people can see me.
Scripture taken from the Good News Translation - Second Edition, Copyright 1992 by American Bible Society. Used by Permission.