Ante-Nicene Fathers, Vol IX:
The Epistles of Clement.: Chapter XL

Chapter XL.—Let Us Preserve in the Church the Order Appointed by God.

These things therefore being manifest to us, and since we look into the depths of the divine knowledge, it behoves us to do all things in [their proper] order, which the Lord has commanded us to perform at stated times. 4216   He has enjoined offerings [to be presented] and service to be performed [to Him], and that not thoughtlessly or irregularly, but at the appointed times and hours.  Where and by whom He desires these things to be done, He Himself has fixed by His own supreme will, in order that all things, being piously done according to His good pleasure, may be acceptable unto Him. 4217   Those, therefore, who present their offerings at the appointed times, are accepted and blessed; for inasmuch as they follow the laws of the Lord, they sin not.  For his own peculiar services are assigned to the high priest, and their own proper place is prescribed to the priests, and their own special ministrations devolve on the Levites.  The layman is bound by the laws that pertain to laymen.

Footnotes

Some join κατὰ καιροὺς τεταγμένους, “at stated times,” to the next sentence.

Literally, “to His will.”