Hadith on Friendship: The Prophet would be kind to his wife’s friends even after she passed way

Anas ibn Malik reported: Whenever the Prophet, peace and blessings be upon him, was given something, he would say, “Go to so-and-so, for she was a friend of Khadija. Go to so-and-so, for she loved Khadija.”

Source: Al-Adab Al-Mufrad 232

Grade: Hasan (fair) according to Al-Bukhari

عَنْ أَنَسٍ قَالَ‏ كَانَ النَّبِيُّ صلى الله عليه وسلم إِذَا أُتِيَ بِالشَّيْءِ يَقُولُ‏ اذْهَبُوا بِهِ إِلَى فُلاَنَةٍ فَإِنَّهَا كَانَتْ صَدِيقَةَ خَدِيجَةَ‏ اذْهَبُوا بِهِ إِلَى بَيْتِ فُلاَنَةٍ فَإِنَّهَا كَانَتْ تُحِبُّ خَدِيجَةَ‏

221 الأدب المفرد البخاري بَابُ قَوْلِ الْمَعْرُوفِ