(Exodus, Ibid.) "the timbrel in her hand": Whence did they have timbrels and dance (instruments) in the desert? — Being tzaddikim, and knowing for a certainty that the Holy One Blessed be He would perform miracles and mighty acts for them when they left Egypt, they readied timbrels and (dance) instruments for themselves.
Knew with Absolute Certainty That God Would Perform Miracles
Mekhilta Tractate Shirah 10:16