Judges 5:5 - Joseph Benson’s Commentary on the Old and New Testaments

The mountains melted Or flowed with floods of water, poured out of the clouds upon them, and from them flowing down in mighty streams upon the lower grounds, and carrying down part of the mountains with them. Even that Sinai Or rather, As did Sinai itself. The whole verse might be better translated, The mountains flowed down at the presence of Jehovah; as did Sinai itself at the presence of Jehovah, the God of Israel. And Dr. Kennicott supposes that, when the ode was sung, the first clause was uttered by Deborah, the second by Barak, and that they both joined in the third. The prophetess here slides into the mention of a more ancient appearance of God for his people at Sinai, it being usual with the inspired writers, in repeating former actions, to put divers together in a narrow compass. The sense is, No wonder that the mountains of the Amorites and Canaanites melted and trembled, when thou didst lead thy people toward them; for even Sinai itself could not bear thy presence, but melted in like manner before thee.