When I came from Ethiopia (to Medina), I was a young girl. Allah's Messenger (ﷺ) made me wear a sheet having marks on it. Allah's Messenger (ﷺ) was rubbing those marks with his hands saying, "Sanah! Sanah!" (i.e. good, good).
Sahih al-Bukhari Book 63, Hadith 99
← Previous Hadith Um Habiba and Um Salama mentioned a church they had seen in Ethiopia and in the church there were pictures. When they told the Prophet (ﷺ) of this, he said, "Those people are such that if a pious man amongst them died, they build a place of worship over his grave and paint these pictures in it. Those people will be Allah's worst creatures on the Day of Resurrection . "

Sahih al-Bukhari Book 63, Hadith 98 Next Hadith → We used to greet the Prophet (ﷺ) while he used to be in prayers, and he used to reply to our greetings. But when we came back from Najashi (the King of Ethiopia) we greeted him (while he was praying) and he did not reply to us. We said, "O Allah's Messenger (ﷺ)! We used to greet you in the past and you used to reply to us." He said, "Verily The Mind is occupied and busy with more important matter during the prayer." (So one cannot return One's greetings.)

Sahih al-Bukhari Book 63, Hadith 100