Here is one of the oldest (and simplest) benediction - in Sanskrit.

सर्वे भवन्तु सुखिनः सर्वे सन्तु निरामयाः।

सर्वे भद्राणि पश्यन्तु मा कश्चिद्दुःखभाग् भवेत्।।

English Transliteration

sarve bhavantu sukhinaḥ sarve santu nirāmayāḥ|

sarve bhadrāṇi paśyantu mā kaścidduḥkhabhāg bhavet||

Meaning in English

May all be happy; May all be healthy.

May all see good; May none partake suffering.

Source - unknown !