Bukhari

Hadith Commentary:
In this chapter of the hadith, asking (begging) has also been condemned, and it has been explained that those who ask without being deserving will be raised on the Day of Resurrection in such a state that there will be no flesh on their faces, and with this disgrace and humiliation, they will be gathered in the plain of resurrection.

Regarding the details of asking, Allamah ‘Ayni rahimahullah says:
وَهِي على ثَلَاثَة أوجه:
حرَام ومكروه ومباح. فالحرام لمن سَأَلَ وَهُوَ غَنِي من زَكَاة أَو أظهر من الْفقر فَوق مَا هُوَ بِهِ. وَالْمَكْرُوه لمن سَأَلَ وَعِنْده مَا يمنعهُ عَن ذَلِك وَلم يظْهر من الْفقر مَا هُوَ بِهِ، والمباح لمن سَأَلَ بِالْمَعْرُوفِ قَرِيبا أَو صديقا. وَأما السُّؤَال عِنْد الضَّرُورَة فَوَاجِب لإحياء النَّفس. وَأدْخلهُ الدَّاودِيّ فِي الْمُبَاح. وَأما الْأَخْذ من غير مَسْأَلَة وَلَا إشراف نفس فَلَا بَأْس بِهِ. (Ayni)

That is, there are three types of asking (begging):
Forbidden (haram), disliked (makruh), and permissible (mubah).

Forbidden is for the one who, despite being wealthy, asks from zakat or unnecessarily portrays himself as needy.

Disliked is for the one who asks for something while he already possesses it, and he does not consider that he already has this thing, and at the same time, he does not even portray himself as needy, yet he asks.

Permissible is for the one who, at the time of genuine need, asks from a close friend or relative.

Sometimes, in the case of extreme necessity where the matter is of life and death, asking also becomes obligatory (wajib) to save a life, and Dawudi has included this in the permissible (mubah). And as for taking something without asking and without coveting it, there is no harm in it.

Along with the mention of the punishment for undeserving beggars, this hadith also mentions the greatest intercession (shafa‘at kubra) of the Prophet sallallahu alayhi wa sallam, which he will be granted on the Day of Resurrection.

Where no other prophet or messenger will have the courage to speak, there the Prophet sallallahu alayhi wa sallam will appear as the intercessor and the one whose intercession is accepted for mankind.

Allahumma grant us the intercession of Your beloved sallallahu alayhi wa sallam on the Day of Resurrection.
Ameen

Hadith Commentary:
(1)
The essence of this hadith is that whoever begs from people not out of necessity but in order to increase his wealth will be utterly humiliated and disgraced on the Day of Resurrection. As a punishment for asking people without any genuine need, the radiance of his face will be taken away, and only bones will remain. In such a dreadful and repulsive form, he will be presented before Allah on the Day of Resurrection. At that time, the torment will be such that the sun will be brought extremely close, and its heat and intensity will burn his bones to ashes. Imam Bukhari rahimahullah has mentioned the hadith of intercession in this context. In contrast, the one who asks out of compulsion, while being in severe need, will be safe from such punishment, because for such a person, asking is permissible (mubah). (: Fath al-Bari: 3/427)

(2)
The suspended narration of Mu‘alla ibn Asad has been narrated by Imam Bayhaqi rahimahullah with his connected chain, whose wording is that whoever constantly begs from people will meet Allah in such a state that there will not even be a piece of flesh on his face. In this narration, there is no mention of the sun being brought near or of intercession, etc. (: al-Sunan al-Kubra lil-Bayhaqi: 4/196, ‘Umdat al-Qari: 6/506)