The International Q Project reconstructs the original Q saying as follows:
Everything has been entrusted to me by my Father,
and no one knows the Son except the Father,
nor [does anyone know] the Father except the Son,
and to whomever the Son chooses to reveal him.
From ['The Five Gospels'] (page 182):
This language is more typical of the Fourth Gospel (3:35; 7:29; 13:3) than it is of anything attributed to Jesus in the synoptic gospels. Christian claims made on Jesus' behalf after his death led to this chain of privileged information—Father to son to disciple. The same language is faintly echoed in Thom 61:3. In all of its versions it was accorded a black designation.
Samuel T. Lachs
Lachs ['Rabbinic Commentary on the New Testament'], (279) notes that "Lord of heaven and earth" is similar to the frequent expression in rabbinic Hebrew: ribono shel olam, 'lord of the world.'
He also notes the anti-Christian polemic:
R. Johanan said: 'From the time of the destruction of the Temple prophecy was taken from prophets and given to children and fools.' (B. BB. 12b)
Luedemann ['Jesus'] (330f), invokes the classic description from K. Hase of this passage as a "thunderbolt from the Johannine heavens." He notes the typically Johannine reference to mutual knowledge between Father and Son, and the absolute use of "Son" as a designation for Jesus. In dismissing the saying's authenticity, Luedemann also notes the similarity to ideas in the post-Easter commissioning scene at Matt 28:18, "All authority has been given to me ..."