Albert Barnes Commentary Leviticus 24:12

"And they put him in ward, that it might be declared unto them at the mouth of Jehovah." — Leviticus 24:12 (ASV)

The offender may already have been pronounced guilty by the rulers , and the case was referred to Moses in order that the punishment might be awarded by the divine decree. No law had yet been enacted against blasphemy except by implication. See Exodus 21:17; Exodus 22:28.