What's the difference between לֹ֥֖א and אַל? For example, in Exodus 20 the Lord repeatedly states, "thou shalt not לֹ֥֖א ..." (see vss. 3-4, 7, 13-17). However, in contrast, Moses states in Exodus 20:20 "Do not אַל be afraid..."
It is in general a difference in pragmatic force. לֹ֥֖א belongs to the "language of the law". It expresses prohibitions that one should always observe: "you shall not commit murder" Ex 20:12 לֹא תִּרְצָֽח׃. Whereas אַל is more dependent on the context, and can be also a simple request in prayer: "don't kill me [make not bare my soul Young's Literal Translation]" Ps 141:8 אַל־תְּעַר נַפְשִֽׁי).
For more detailed information you can have a look at the online Gesenius' Hebrew Grammar available at https://en.wikisource.org/wiki/Gesenius%27_Hebrew_Grammar/152._Negative_Sentences