Rule 1: 1. لَمْ يَجِئْ and لَمْ يَشَأْ
In the jussive the hollow verb shortens its long vowel because the last syllable is closed; the final hamza then sits on the letter that matches the preceding short vowel. يَجِيءُ → لَمْ يَجِئْ (hamza on a ي-seat after kasra); يَشَاءُ → لَمْ يَشَأْ (hamza on alif after fatḥa). The perfect shortens with i, as in سِرْتُ and خِفْتُ: جِئْتُ، شِئْتَ.
اِنْتَظَرْتُهُ سَاعَةً وَلَمْ يَجِئْ.
intaẓartuhu sāʿatan wa-lam yajiʾ
I waited an hour for him and he did not come.
لَمْ أَشَأْ أَنْ أُزْعِجَكَ.
lam ashaʾ an uzʿijaka
I did not want to disturb you.
جِئْتُ بِالدَّوَاءِ مُسْرِعًا.
jiʾtu bi-d-dawāʾi musriʿan
I brought the medicine in a hurry.
جَاءَ بِـ 'to bring', like أَتَى بِـ.
اِفْعَلْ مَا شِئْتَ.
ifʿal mā shiʾta
Do whatever you wish.