Buying from a grocery store on credit is not regarded as riba al-nasee’ah
Question

                There is a grocery store near our house and we ask them for what we want from them, and delay paying the price until a certain time. Is this regarded as riba al-nasee’ah? Please note that the vendor agrees to any method of paying, whether sooner or later. What is the ruling on that?.
Praise be to Allah.
    Buying things from the grocery store and delaying payment is 
    not regarded as riba at all. 

    That is because the types of things narrated from the Prophet 
     (peace and blessings of Allaah be upon him) which may be subject to 
    riba are six things: gold and silver (to which cash is added nowadays), and 
    dates, wheat, barley and salt. 

    The scholars divided these types into two categories, 
    according to the reason for which riba is used: 

    1 – Gold and silver, etc.

    2 – Wheat, barley, dates and salt. 

    If a person wants to buy something from the second category 
    in return for something from the first category, such as if he wants to buy 
    dates for cash, then there is no riba involved, and it is permissible to buy 
    it with a delay in payment, according to scholarly consensus. 

    The Prophet  (peace and blessings of Allaah be upon him) 
    bought some barley from a Jew, and delayed payment of the price, and he left 
    his shield with him as collateral. 

    It was narrated that ‘Aa’ishah (may Allaah be pleased with 
    her) said: The Messenger of Allaah  (peace and blessings of Allaah be 
    upon him) bought some food on credit from a Jew, and he gave him a shield of 
    his as collateral (rahn). Narrated by al-Bukhaari (1999) and Muslim (1603). 

    Al-Bukhaari narrated it from Anas (may Allaah be pleased with 
    him) in the words: The Prophet  (peace and blessings of Allaah be upon 
    him) left his shield as collateral with a Jew in Madeenah and took some 
    barley from him for his family. 

    Al-Bukhaari included this report in a chapter entitled “The 
    Prophet  (peace and blessings of Allaah be upon him) bought on credit.” 

    Ibn Hajar said: 

    Ibn Battaal said: Buying on credit is permissible according 
    to scholarly consensus. 

    Fath al-Baari (4/302). 

    So it is permissible for you to buy things from the grocery 
    store and delay payment of the cash, and that does not come under the 
    heading of riba al-nasee’ah. 

    And Allaah knows best.