Hadithcore
Mishkat al-Masabih, 1590, 1591

Anas reported God's messenger as saying, “A visit should last as long as the time between the two milkings of a she-camel.”(The reference is to the practice of drawing some milk from the camel, then leaving her for a little for her young to suck milk. When she then let her milk flow copiously she was milked again.) In the version of Sa'id b. al-Musayyib in <i>mursal</i> form it says, “The best type of sick visit is when one gets up and departs soon.”(While this is more explicit to one who is not familiar with the milking of camels, the meaning is the same as in the form given by Anas.) Baihaqi transmitted it in <i>Shu'ab al-iman</i>.

وَعَنْ أَنَسٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى الله عَلَيْهِ وَسلم: «العيادة فوَاق نَاقَة» وَفِي رِوَايَةِ سَعِيدِ بْنِ الْمُسَيَّبِ مُرْسَلًا: «أَفْضَلُ الْعِيَادَةِ سُرْعَةُ الْقِيَامِ» . رَوَاهُ الْبَيْهَقِيُّ فِي شُعَبِ الْإِيمَان

References1 variant
In-Book Reference
Book 5, Hadith 68