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Zaid b. Thabit (Allah be pleased with him) said: We took meal shortly before dawn along with the Messenger of Allah (ﷺ). We then stood up for prayer. I said: How much span of time was there between the two (acts, i. e. taking of Sahri and observing of prayer)? He said (a span of reciting) fifty verses.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعٌ، عَنْ هِشَامٍ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، عَنْ زَيْدِ بْنِ ثَابِتٍ، - رضى الله عنه - قَالَ تَسَحَّرْنَا مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم ثُمَّ قُمْنَا إِلَى الصَّلاَةِ . قُلْتُ كَمْ كَانَ قَدْرُ مَا بَيْنَهُمَا قَالَ خَمْسِينَ آيَةً .
sunnah.com