Common mistakes
The middle radical is و or ي. It stretches into a long vowel: قَالَ: and shortens before a consonant ending and in the jussive: قُلْتُ, لَمْ يَقُلْ.
اِسْتَقْيَلَ → اِسْتَقَالَ Past: heاِسْتَقْيَلَتْ → اِسْتَقَالَتْ Past: sheاِسْتَقْيَلْتَ → اِسْتَقَلْتَ Past: you (m.)اِسْتَقْيَلْتُ → اِسْتَقَلْتُ Past: I