Matthew 27:43 - Ellicott's Commentary On The Whole Bible

Let him deliver him now. — It seems at first hardly conceivable that priests and scribes could thus have quoted the very words of Psalms 22:8, and so have fulfilled one of the great Messianic prophecies. But (1) we must remember that they, ignoring the idea of a suffering Christ, would not look on the Psalm as Messianic at all, and (2) that their very familiarity with the words of the Psalm would naturally bring its phraseology to their lips when occasion called for it. Only they would persuade themselves that they were right in using it, while David’s enemies were wrong.