Ruling on singling out Fridays for visiting graves

There is no basis for that. What is prescribed is to visit graves at any time of night or day that suits the visitor. With regard to singling out a particular day or night, this is bid’ah and there is no basis for this, because the Prophet (peace and blessings of Allah be upon him) said: “Whoever innovates anything in this matter of ours (Islam) that is not a part of it will have it rejected.” (Saheeh, agreed upon). And he (peace and blessings of Allah be upon him) said: “Whoever does anything that is not a part of this matter of ours (Islam) will have it rejected.” (narrated by Muslim in his Saheeh from ‘Aa’ishah, may Allah be pleased with her).