Psalms 68:8 - Coke's Commentary on the Holy Bible

The earth shook, &c.— When the people arrived at Sinai, and God descended on the mountain, the earth trembled at his presence; the heavens also dropped, i.e. dissolved into showers, as the consequence of the mighty thunders and lightnings which bespoke the presence of the Almighty, and of the thick cloud which covered the mount. Exodus 19:16. In the next clause, Even Sinai itself, &c. one of the verbs in the former clauses must be supplied: Sinai itself shook, or dropped at the presence of God: that is, as it were, flowed down and dissolved. So Deborah, Joshua 5:4-5 in her song of triumph says, Lord, when thou wentest out of Seir, when thou marchedst from the field of Edom; the earth trembled, and the heavens dropped; the clouds also dropped down water. The mountains flowed down at the presence of the Lord; this Sinai [flowed down] at the presence of the God of Israel.