A dagesh in an alef is a very rare occurence, but it does happen at least 4 times that I know of (jk, I googled it). One is in the word ????? in the above pasuk in parshas emor which Geordie brought down and the Wolf cited. The second is the word ?????? in mikeitz (?????? ??:??), when Yosef’s brothers came to him a second time, with Binyamin, and they brought Yosef a gift. Another time is in sefer Ezra, ?:??, also with the word ??????, and the last time is in Iyov, ??:??, with the word ???.
“On the pasuk in Emor, Shemen Hamor comments that there is a dagesh in the aleph for the purpose of tiferes halashon, beautification of the language. Minchas Shai notes in Emor that this is one of the alfin degushin, that he speaks about it in more details in Bereishit 2:25, on vayihyu sheneihem arumim, and that he gives the masorah for this in Miketz, on Bereishit 43:26. Read what Minchas Shai has to say in each of these three locations.”
Although I can’t cite my sources with a simple website link, copy and paste will help you find what I found. It’s called parshablog, and the blogger goes into exhaustive detail over the dikduk. It’s REALLY cool.