Wong Tsun Wah Leo

“One standard Jewish prayer of the day (the Kaddish) proclaimed, “Exalted and hallowed be his . . . name . . . and may his kingdom come speedily and soon.” Because God was Father, his children could depend on him (cf. 18:3).”
― Craig S. Keener, The IVP Bible Background Commentary: New Testament

“Jewish people commonly addressed God as “our heavenly Father” when they prayed, although such intimate titles as “Abba” (Papa) were rare (see comment on Mk 14:36).”
― Craig S. Keener, The IVP Bible Background Commentary: New Testament

“6:9-10. Greek sources often called the supreme deity “father,” including in prayers, but this practice is pervasive in Jewish sources as well, even as early as the *Old Testament (Deut 32:6; Ps 68:5; Is 63:16; 64:8; Jer 3:4, 19; 31:9; Mal 1:6; 2:10) and other very early Jewish works (e.g., Tobit 13:4; *3 Maccabees 5:7; 7:6).”
― Craig S. Keener, The IVP Bible Background Commentary: New Testament