The word(s) "two-thirds" appears 3 time(s) in 3 verse(s) in Quran in Muhammad Pickthal translation.

(1) Allah chargeth you concerning (the provision for) your children: to the male the equivalent of the portion of two females, and if there be women more than two, then theirs is two-thirds of the inheritance, and if there be one (only) then the half. And to each of his parents a sixth of the inheritance, if he have a son; and if he have no son and his parents are his heirs, then to his mother appertaineth the third; and if he have brethren, then to his mother appertaineth the sixth, after any legacy he may have bequeathed, or debt (hath been paid). Your parents and your children: Ye know not which of them is nearer unto you in usefulness. It is an injunction from Allah. Lo! Allah is Knower, Wise.

(2) They ask thee for a pronouncement. Say: Allah hath pronounced for you concerning distant kindred. If a man die childless and he have a sister, hers is half the heritage, and he would have inherited from her had she died childless. And if there be two sisters, then theirs are two-thirds of the heritage, and if they be brethren, men and women, unto the male is the equivalent of the share of two females. Allah expoundeth unto you, so that ye err not. Allah is Knower of all things.

(3) Lo! thy Lord knoweth how thou keepest vigil sometimes nearly two-thirds of the night, or (sometimes) half or a third thereof, as do a party of those with thee. Allah measureth the night and the day. He knoweth that ye count it not, and turneth unto you in mercy. Recite, then, of the Qur'an that which is easy for you. He knoweth that there are sick folk among you, while others travel in the land in search of Allah's bounty, and others (still) are fighting for the cause of Allah. So recite of it that which is easy (for you), and establish worship and pay the poor-due, and (so) lend unto Allah a goodly loan. Whatsoever good ye send before you for your souls, ye will find it with Allah, better and greater in the recompense. And seek forgiveness of Allah. Lo! Allah is Forgiving, Merciful.