35 cards where the full Oracle text includes “flanking”

Agility (Mirage #154)
Barbed Foliage (Mirage #207)
Benalish Cavalry (Time Spiral Remastered #7)
Blazing Blade Askari (Time Spiral #146)
Bogardan Lancer (Future Sight #95)
Burning Shield Askari (Mirage #162)
Cadaverous Knight (Planechase #20)
Cavalry Master (Time Spiral #6)
Fallen Askari (Vintage Masters #119)
Femeref Knight (Mirage #18)
Flanking Troops (Portal Three Kingdoms #5)
Gustcloak Cavalier (Time Spiral #22)
Jabari's Banner (Weatherlight #150)
Jolrael's Centaur (Mirage #222)
Knight of Sursi (Time Spiral Remastered #22)
Knight of the Holy Nimbus (Time Spiral Remastered #23)
Knight of the Mists (Visions #36)
Knight of Valor (Visions #11)
Mtenda Herder (Mirage #29)
Old Fogey (Unsanctioned #67)
Outrider en-Kor (Time Spiral Remastered #30)
Pentarch Paladin (Time Spiral #32)
Riftmarked Knight (Time Spiral Remastered #38)
Searing Spear Askari (Mirage #191)
Shadow Rider (Weatherlight #79)
Sidar Jabari (Vintage Masters #45)
Sidar Kondo of Jamuraa (Murders at Karlov Manor Commander #219)
Sidewinder Sliver (Time Spiral Remastered #43)
Skulking Knight (Time Spiral #130)
Suq'Ata Lancer (Dominaria Remastered #145)
Teferi's Honor Guard (Visions #22)
Telim'Tor (Mirage #197)
Zhalfirin Commander (Duel Decks: Knights vs. Dragons #13)
Zhalfirin Crusader (Vintage Masters #54)
Zhalfirin Knight (Mirage #50)

This search is finished. Now the real work can begin.