فَلَمَّا جَاوَزَاSo when they had passed further on,means, past the place where they had forgotten the fish.Forgetfulness is attributed to them both even though it was actually Yusha` who forgot.This is like the Ayah:يَخْرُجُ مِنْهُمَا الُّلوْلُوُ وَالمَرْجَانُOut of them both come out pearl and coral. (55:22),although they come from the salt water, according to one of the two opinions.When they had passed one stage beyond the place where they had forgotten the fish,قَالَ لِفَتَاهُ اتِنَا غَدَاءنَا لَقَدْ لَقِينَا مِن سَفَرِنَا هَذَا(Musa) said to his boy-servant:�Bring us our morning meal; truly, we have suffered in this, our journey,meaning, their journey beyond the place where they should have stopped.نَصَبًاNasaban,means, exhaustion.