What did the fifth-seal martyrs have to wait for before their time of rest ended?
The fifth-seal martyrs were told to rest a little season until their fellow servants and brethren who would be killed as they had been were fulfilled—that is, until the full number of those martyred for their faith was completed.
Les explains that John sees these martyred believers in a prophetic light. White robes were given to each of them, for they had been martyred for their faith. They were then told they should rest yet for a little season, until their fellow servants also, and their brethren that should be killed as they were, should be fulfilled. Les notes that this entire statement is part of the fifth seal. After that, the sixth seal is opened and brings a great earthquake, which connects with Jesus' words in Matthew 24 about earthquakes in diverse places.