The word(s) "mother's" appears 4 time(s) in 3 verse(s) in Quran in Muhammad Pickthal translation.

(1) And unto you belongeth a half of that which your wives leave, if they have no child; but if they have a child then unto you the fourth of that which they leave, after any legacy they may have bequeathed, or debt (they may have contracted, hath been paid). And unto them belongeth the fourth of that which ye leave if ye have no child, but if ye have a child then the eighth of that which ye leave, after any legacy ye may have bequeathed, or debt (ye may have contracted, hath been paid). And if a man or a woman have a distant heir (having left neither parent nor child), and he (or she) have a brother or a sister (only on the mother's side) then to each of them twain (the brother and the sister) the sixth, and if they be more than two, then they shall be sharers in the third, after any legacy that may have been bequeathed or debt (contracted) not injuring (the heirs by willing away more than a third of the heritage) hath been paid. A commandment from Allah. Allah is Knower, Indulgent.

(2) Forbidden unto you are your mothers, and your daughters, and your sisters, and your father's sisters, and your mother's sisters, and your brother's daughters and your sister's daughters, and your foster-mothers, and your foster-sisters, and your mothers-in-law, and your step-daughters who are under your protection (born) of your women unto whom ye have gone in - but if ye have not gone in unto them, then it is no sin for you (to marry their daughters) - and the wives of your sons who (spring) from your own loins. And (it is forbidden unto you) that ye should have two sisters together, except what hath already happened (of that nature) in the past. Lo! Allah is ever Forgiving, Merciful.

(3) O Prophet! Lo! We have made lawful unto thee thy wives unto whom thou hast paid their dowries, and those whom thy right hand possesseth of those whom Allah hath given thee as spoils of war, and the daughters of thine uncle on the father's side and the daughters of thine aunts on the father's side, and the daughters of thine uncle on the mother's side and the daughters of thine aunts on the mother's side who emigrated with thee, and a believing woman if she give herself unto the Prophet and the Prophet desire to ask her in marriage - a privilege for thee only, not for the (rest of) believers - We are Aware of that which We enjoined upon them concerning their wives and those whom their right hands possess - that thou mayst be free from blame, for Allah is ever Forgiving, Merciful.