Bukhari

Hadith Commentary:
The intended meaning is that servant whose beloved child passes away, and he exercises patience—then certainly that child will intercede for him.
But who is there in this world who does not face such a calamity?
Except whom Allah wills.
May Allah also grant me the ability to be patient, ameen. (Raaz)

Hadith Commentary:
(1)
A believer can hope for reward in every action, provided that the intention is to seek reward. This intention has been termed "ihtisab" (seeking reward) by the Shari‘ah. In fact, even in every calamity and hardship, if one is patient with the intention of seeking reward, then there is also a promise of reward in that, as mentioned in the above hadith.
(2)
It should be clear that in the hadith, the term "beloved thing" is general in meaning, whether it is a dear child or any other beloved possession. On this basis, if someone’s child passes away or he loses his eyesight, and he is patient over it with the intention of seeking reward, then Allah Ta‘ala has promised him Paradise. Accordingly, it is mentioned in the hadith that a man used to come to the Messenger of Allah (sallallahu alayhi wa sallam), and his young son would come with him. For a few days, he was absent from your gathering, so the Messenger of Allah (sallallahu alayhi wa sallam) inquired about him. The people informed him that his son had passed away, and that is why he was distressed. The Messenger of Allah (sallallahu alayhi wa sallam) said:
“Does he not like that whenever he comes to any gate of Paradise, he finds his son waiting for him there?” Upon hearing this glad tidings, a man said: “O Messenger of Allah! Is this good news only for that man?” He (sallallahu alayhi wa sallam) replied: “It is for all of you.”
(Musnad Ahmad: 3/436)