Kissing the Thumbs on the name of Muhammad
Kissing the thumbs or the index fingers and putting them to the eyes on hearing the name of the beloved Muhammad, intercessor on the day of Judgement, in the Adhaan is absolutely permissible, good and a source of great mercy and barakah.
Whilst there is no evidence prohibiting it there are many proofs for it. Here are some proofs for the reader: thumbs.pdf