Matsyapurana 16.20

16.20

akrodhanaiḥ śaucaparaiḥ satataṃ brahmacāribhiḥ
bhavitavyaṃ bhavadbhiśca mayā ca śrāddhakāriṇā //

The guests to the Śrâddha feast should be courteously invited the same day or a day previous to the feast. The Pitṛis accompany the invited twice-born, in the form of air, and sit along with them at the time of the feast. The host should go and invite his twice-born guest by touching his right knee and address him thus "thou hast been invited by me, accept my invitation." After thus addressing, he should remind the guest as well as his paternal kinsmen in these words:—"You should be without anger, observe purity and rules of continence the whole of this day, and I the performer of Śrâddha would also observe the same along with you."—18-20.