﴿ يَٰوَيْلَتَىٰ لَيْتَنِى لَمْ أَتَّخِذْ فُلَانًا خَلِيلًۭا ﴾

“Oh, woe is me! Would that I had not taken so-and-so for a friend!”

O woe to me! yā waylatā the final alif stands in place of the first person singular possessive yā’ yā waylatī meaning ‘alas for my destruction!’ Would that I had not taken so and so in other words that Ubayy as friend!