Isaiah 40:3
1 “Comfort, comfort my people,” says your God. 2 “Speak kindly to Jerusalem and tell her that her time of warfare is over, that her punishment is completed. For the Lord has made her pay double for all her sins.” 3 A voice cries out, “In the wilderness clear a way for the Lord; build a level road through the rift valley for our God. 4 Every valley must be elevated and every mountain and hill leveled. The rough terrain will become a level plain, the rugged landscape a wide valley. 5 The splendor of the Lord will be revealed, and all people will see it at the same time. For the Lord has decreed it.”
Psalms of Solomon 8:17
15 He brought the one from the end of the earth, the mighty warrior, he declared war against Jerusalem, and against her land. 16 The leaders of the country met him with joy. They said to him, 'Welcome, we have expected you. Come, all of you, enter in peace.' 17 They graded the rough roads for his coming; they opened the gates to Jerusalem, they lined her walls. 18 He entered peacefully, like a father into his sons' house; he secured a foothold. 19 He pulled down her battlements and the wall of Jerusalem, for God led him in unscathed in their confusion.
Notes and References
"... Bradley H. McLean, Citations and Allusions to Jewish Scripture in Early Christian and Jewish Writings Through 180 C.E. (Lewiston, N.Y.: Edwin Mellen Press, 1992), 90, also lists Psalms of Solomon 8:17 and Sibyllene Oracles 1:336, but the latter is a Christian text reflecting New Testament usages of the Isaian verse. In contrast to my argument here, Ian McDonald plays down the relevance of the fact that both the Qumranians and John the Baptist associated themselves with Isaiah 40:3, claiming that “this text represents a well known crux interpretum, and it seems likely that John read the text in a different way” ..."
Marcus, Joel John the Baptist in History and Theology (p. 177) The University of South Carolina Press, 2018