"And he was, in the sight of his Lord, well-pleasing," meaning: He was pleased with him [when He tested him with the sacrifice].
﴿وَكَانَ عِنْد ربه مرضيا﴾ أَيْ: قَدْ رَضِيَ عَنْهُ [إِذِ ابتلاه بِالذبْحِ]
