It's very integersting expression: "air do X" as "while X was doing something" or "X, having done something".Agus air do Pheadar sealltainn gu geur air, maille ri Eòin, thubhairt e, Amhairc oirnne (3:4)
And fixing his eyes on him, with John, Peter said, “Look at us.”
Agus air dha breith air a làimh dheis, thog e suas e (3:7)
And he took him by the right hand and lifted him up
Air do Dhia a Mhac Iosa a thogail suas, chuir e dur n-ionnsaigh-se e air tùs, a-chum gum beannaicheadh e sibh (3:26)
To you first, God, having raised up His Servant Jesus, sent Him to bless you
Is it very old-fasioned? Is it quite understandable now or not?