It's short for いて, the て form of いる. I'm sure you're aware that て form on its own is a light command. So 待って(い)て is like "stay here and wait", while just 待って without いる would be just "wait."
空に祈るだけで晴れにできるって Can someone explain the って at the end of the sentence !
Hi embarc, sure. This って is often used in casual speech and is here standing for the particle と (as in "と言う") so it expresses something like "was said by X / someone". It is quite flexible and can be used for many different things, and is also very common, so I would suggest you study it a bit more, for example starting here: https://www.imabi.net/ttetattedatte.htm
As for your sentence, the translation can vary quite a bit depending on the context because of this, but it's something like "They claimed they can turn the sky clear just by praying." (they could be singular or plural).
Sentence-final て
郵便局に行って来なくちゃなんないから、ちょっとここで待ってて。
Can someone explain the second て at the end of the sentence for me? Thanks.