Hazrat Abu Bakr Siddeeq (radhiyallahu ‘anhu) relates the following regarding the journey of hijrah with Hazrat Rasulullah (sallallahu ‘alaihi wasallam):
We travelled hastily the entire night and part of the following day until the afternoon heat became intense. I then found the road to be empty with no one walking on it. I looked ahead to see whether I could find any shade so that we could take shelter in it. I then spotted a large rock under which there was some shade in which we could take refuge and seek shelter from the heat.
We stopped by the rock (to rest in its shade), and I used my hands to make the ground flat so that Rasulullah (sallallahu ‘alaihi wasallam) could lie down and rest. I then spread out a leather skin and said to him, “Rest, O Rasul of Allah (sallallahu ‘alaihi wasallam), and I will keep watch on the area around you.”
Once Rasulullah (sallallahu ‘alaihi wasallam) lay down to rest, I went to see whether I could spot anyone who was searching for us. I then caught sight of a slave shepherd coming towards the rock so that he may also rest in the shade, as we were resting.
I asked him who his owner was, and he named a man from Makkah whom I knew. (As it was a prevalent custom at that time that people would allow travellers and wayfarers to benefit from the milk from their flock, Hazrat Abu Bakr Siddeeq I asked the shepherd for some milk.)
Hazrat Abu Bakr Siddeeq (radhiyallahu ‘anhu) says:
I asked the shepherd, “Do any of the goats have milk?” The shepherd replied, “Yes.” I then asked him, “Will you milk a goat for me?”
The shepherd agreed, but before he could milk the goat, I said to him, “Ensure that you first dust the goat’s udders and clean them from dust, hair and other dirt.” The shepherd then milked the goat and poured the milk into my container. I added some water to the milk to cool the hot milk. I then took the milk to present it to Rasulullah (sallallahu ‘alaihi wasallam). I did not wish to disturb the sleep of Rasulullah (sallallahu ‘alaihi wasallam) by waking him up, but when I reached, I found him awake.
I then presented the milk to him saying, “Partake of this, O Rasulullah (sallallahu ‘alaihi wasallam).” The sight of Rasulullah (sallallahu ‘alaihi wasallam) relishing the milk brought extreme joy and happiness to my heart.
From this incident, we see the great love which Hazrat Abu Bakr (radhiyallahu ‘anhu) had for Rasulullah (sallallahu ‘alaihi wasallam), that the sight of Rasulullah (sallallahu ‘alaihi wasallam) relishing the milk brought great happiness to his heart, whereas he was not the one enjoying the milk.
This can be resembled to the love of a mother for her child when she sees the child relishing food – the sight itself brings joy to her heart.
 صحيح البخاري، الرقم: 3615، صحيح مسلم، الرقم: 3014