In a solemn manner, in various senses of the adjective; ceremoniously, formally; gravely, seriously, etc.

Solemnly; ceremoniously.

In accordance with rites; with due form.

solemnly. Obsolete.

Solemnly.

In a ceremonious manner; formally, in due form; with strict observance of formalities; †in accordance with the Ceremonial Law (obsolete).

In accordance with ritual or custom; in a ritual way.

In a ceremonial manner; in relation to ceremonies or the ceremonial law.

from a liturgical point of view; in a liturgy, in liturgical worship.