Allah's statement,

ثُلَّةٌ مِّنَ الْأَوَّلِينَ ﴿٣٩﴾

وَثُلَّةٌ مِّنَ الْآخِرِينَ ﴿٤٠﴾

A multitude of those will be from the first generation. And a multitude of those will be from the later generations.

means, a multitude of those on the right will come from the earlier generations and a multitude from the latter generations.

Ibn Abi Hatim recorded that Abdullah bin Mas`ud said,

"We were with the Prophet one night and in the next morning we went to him and he said,

عُرِضَتْ عَلَيَّ الْأَنْبِيَاءُ وَأَتْبَاعُهَا بِأُمَمِهَا، فَيَمُرُّ عَلَيَّ النَّبِيُّ، وَالنَّبِيُّ فِي الْعِصَابَةِ، وَالنَّبِيُّ فِي الثَّلَاثَةِ، وَالنَّبِيُّ وَلَيْسَ مَعَهُ أَحَد

Some Prophets and their nations were displayed before me. A Prophet would pass in front of me with a group of men, and another with three men, and another with nobody with him.

Qatadah, one of the narrators of the Hadith, then recited this Ayah,

أَلَيْسَ مِنْكُمْ رَجُلٌ رَّشِيدٌ

Is there not among you a single right-minded man, (11:78)

حَتْى مَرَّ عَلَيَّ مُوْسَى بْنُ عِمْرَانَ فِي كَبْكَبَةٍ مِنْ بَنِي إِسْرَائِيل

Until Musa, son of `Imran passed me, with a great crowd from the Children of Israel.

So he said;

قُلْتُ: رَبِّي مَنْ هذَا؟ قَالَ: هذَا أَخُوكَ مُوسَى بْنُ عِمْرَانَ وَمَنْ تَبِعَهُ مِنْ بَنِي إسْرَائِيل

قُلْتُ: رَبِّ فَأَيْنَ أُمَّتِي؟

قَالَ: انْظُرْ عَنْ يَمِينِكَ فِي الظِّرَاب

فَإِذَا وُجُوهُ الرِّجَال

قَالَ: أَرَضِيتَ؟

قُلْتُ: قَدْ رَضِيتُ رَب

انْظُرْ إِلَى الْأُفُقِ عَنْ يَسَارِكَ، فَإِذَا وُجُوهُ الرِّجَال

أَرَضِيتَ؟

قُلْتُ: قَدْ رَضِيتُ رَب

فَإِنَّ مَعَ هؤُلَاءِ سَبْعِينَ أَلْفًا يَدْخُلُونَ الْجَنَّةَ بِغَيْرِ حِسَاب

So, I asked my Lord, "Who is this''

He said, "This is your brother Musa, son of Imran, and those who followed him among the Children of Israel.''

I said, "O Lord! Where is my Ummah''

Allah said, "Look to your right on the hill,''

and I looked and saw faces of men.

Allah said, "Are you pleased,''

and I said, "I am pleased O Lord!''

Allah said, "Look to the horizon to your left,'' and I saw faces of men.

He again asked, "Are you pleased,''

and I said, "I am pleased, O Lord!''

He said, "And with them are seventy-thousand who will enter Paradise without reckoning.''

Ukkashah bin Mihsan from Bani Asad, one of those who participated in the battle of Badr, said, `O Allah's Messenger! Invoke Allah to make me one of them.'

The Prophet said,

اللْهُمَّ اجْعَلْهُ مِنْهُم

O Allah, make him one of them.

Another man said, `O Allah's Messenger, invoke Allah to make me one of them.'

The Prophet said,

سَبَقَكَ بِهَا عُكَّاشَة

Ukkashah beat you to it.

Allah's Messenger said,

فَإِنِ اسْتَطَعْتُمْ فِدَاكُمْ أَبِي وَأُمِّي أَنْ تَكُونُوا مِنْ أَصْحَاب السَّبْعِينَ فَافْعَلُوا، وَإِلَّا فَكُونُوا مِنْ أَصْحَابِ الظِّرَابِ، وَإِلَّا فَكُونُوا مِنْ أَصْحَابِ الْأُفُقِ، فَإِنِّي قَدْ رَأَيْتُ نَاسًا كَثِيرًا قَدْ تَأَشَّبُوا حَوْلَه

Therefore, may I sacrifice my father and mother for you! Try to be among the seventy (thousands), or among the crowds on the right, or the crowds that covered the side of the horizon, because I saw large crowds gathering on that side.

He continued:

إِنِّي لَأَرْجُو أَنْ تَكُونُوا رُبُعَ أَهْلِ الْجَنَّة

I hope that you will be a fourth of the people of Paradise.

and we said, Allahu Akbar.

He said,

إِنِّي لَأَرْجُو أَنْ تَكُونُوا ثُلُثَ أَهْلِ الْجَنَّة

I hope that you will be a third of the people of Paradise.

and we said, Allahu Akbar.

The Prophet said,

إِنِّي لَأَرْجُو أَنْ تَكُونُوا نِصْفَ أَهْلِ الْجَنَّة

I hope that you will be half of the people of Paradise,

and we said Allahu Akbar.

Then Allah's Messenger recited this Ayah:

ثُلَّةٌ مِّنَ الْأَوَّلِينَ - وَثُلَّةٌ مِّنَ الْآخِرِينَ -

A multitude of those will be from the first generation. And a multitude of those will be from the later generations.

We said to each other, `Who are those seventy thousand?'

We then said, `They are those who were born in Islam and did not associate (anything or anyone in the worship of Allah).'

When what we said reached the Prophet, he said,

بَلْ هُمُ الَّذِينَ لَا يَكْتَوُونَ، وَلَا يَسْتَرْقُونَ وَلَا يَتَطَيَّرُونَ، وَعَلَى رَبِّهِمْ يَتَوَكَّلُون

They are the people

- who do not get treated by cauterization themselves,

- do not ask for Ruqyah (get oneself treated by the recitation of some verses of the Qur`an) and

- do not draw an evil omen from (birds), but put their trust (only) in their Lord.''

This Hadith has many chains of narration collected in the Sahihs and other collections of Hadith.