﴿أَمْ حَسِبْتُمْ أَنْ تَدْخُلُوا الْجَنَّةَ وَلَمَّا يَأْتِكُمْ مَثَلُ الَّذِينَ خَلَوْا مِنْ قَبْلِكُمْ﴾
Did you think you would enter Paradise while the like of what befell those before you has not yet come to you? (Al-Baqarah 2:214)
Lammā yaʾtikum explicitly indicates that an expected occurrence has not yet taken place. Its wāw relates this fact to the earlier assumption as a circumstance or contrast. Because lammā changes the temporal force of the imperfect, this should not be confused with the rule for the ordinary affirmative imperfect ḥāl.