金剛般若經疏論纂要 1.159

1.159

於法實無所得者，然燈佛說，說是語言；釋迦所聞，唯聞語言。語言非實，智證法故。論云「釋迦於然燈所，言語所說不取證法，以是義故，顯彼證智不可說、不可取。」

As for "truly attained nothing in regards to the Dharma": what Dīpaṅkara Buddha spoke, the speaking was verbal language; what Śākyamuni heard, he heard only verbal language. Verbal language is not real, because it is wisdom that realizes the Dharma. The commentary says: "At the place of Dīpaṅkara, Śākyamuni did not grasp what was spoken in words as the realized Dharma; through this meaning, it is revealed that that realizing wisdom can neither be explained nor grasped."