مِشْكَاةُ الْمَصَابِيحِ
Mishkat al-Masabih 1587
Funerals
Visiting the Sick, and the Reward for Sickness - Section 3
وَعَنْ أَنَسٍ قَالَ: كَانَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لَا يَعُودُ مَرِيضًا إِلَّا بَعْدَ ثَلَاثٍ. رَوَاهُ ابْنُ مَاجَهْ وَالْبَيْهَقِيُّ فِي شُعَبِ الْإِيمَانِ
Anas said the Prophet (ﷺ) was not accustomed to visit an invalid till he had been ill for three days. Ibn Majah and Baihaqi, in Shu'ab al- iman, transmitted it.
Mishkat al-Masabih, 1587ضَعِيف جدا (الألباني)