“And if they had remained on the way” – meaning upon faith, “We would have given them abundant water” – meaning: We would have expanded their provision; according to the interpretation of al-Hasan.
﴿وألَّوا استقاموا على الطَّرِيقَة﴾ عَلَى الْإِيمَانِ ﴿لأَسْقَيْنَاهُمْ مَاءً غَدَقًا﴾ أَيْ: لَأَوْسَعْنَا لَهُمْ مِنَ الرِّزْقِ؛ فِي تَفْسِير الْحسن