Introduction

This use of لـ is very closely related to the conjunction لاحسن and the two are often interchangeable. The Bedawi/Hines dictionary states that this conjunction is best translated into English as 'lest' and appears frequently after imperatives and forms of the verb خاف. The examples on this page will confirm their explanation and also expand it.
Some things to pay attention to: 1) the clause that لـ precedes often will contain an undesirable situation/ outcome just like the word 'lest'. For this reason one cannot say in English "Come quick lest I give you ice cream". 2) the clause that لـ precedes must have a verb in the plain-form present tense (therefore not a verb with the habitual بـ or future tense هـ / حـ prefix). If it does not, then the helping verb يكون / تكون is used. If the helping verb is used, the لـ usually attaches to it; otherwise; لـ can attach to either the verb or the subject.
Section 1 shows لـ used with commands/requests, Section 2 shows لـ with verbs that express fear, doubt, worry, and Section 3 shows that it can be used in situations outside of those explained by section 1 and 2.

لـ can be used in a sentence where the speaker wants the listener to do something. Such a sentence usually includes a verb in the imperative form or words like اوعى، بلاش، اياكand even words that mark requests like ممكن. When used with commands/requests, لـ precedes the clause that expresses either why the command/request is being given (Examples 1-5) or the punishment for not following the command (Example 6). When لـ precedes a clause explaining why the command is being given, it can be translated as 'because I am/was afraid that....' and when preceding a clause that contains a punishment it can be translated as 'or else.'

Although لـ frequently appears along with the verb خاف, it also can go with verbs that express a similar meaning like قلق and شكّ . The conjunction لـ can continue to be translated as 'lest' but it may also be more natural to translate it as 'that' or even 'because'.The best way to think about لـ with these verbs is that it marks the clause that explains why the speaker is feeling this negative emotion and not the clause that explains the object of the emotion. Therefore, even though both لـ and إن can be translated as 'that' they mark two different things in Egyptian. إن marks the object of these verbs (the thing the speaker is afraid of) and لـ why the speaker is feeling this emotion. Examples 9-11 best show this because the verbs all have direct objects in addition to clauses modified by لـ. When لـ is translated as 'that' notice how it puts the verb into the past tense in the English translation even though it is in the present tense in Egyptian.

We saw above in Section 1 that لـ can be translated as 'because I am afraid that..' when explaining why the command is being given. The example below shows that this definition and use is not restricted to commands.