Seen and heard Sunday at Divine Service

The very beautiful collect for Proper 21:

O God, you declare your almighty power chiefly in showing mercy and pity: Grant us the fullness of your grace, that we, running to obtain your promises, may become partakers of your heavenly treasure; through Jesus Christ our Lord, who lives and reigns with you and the Holy Spirit, one God, for ever and ever. Amen.

Hatchett's Commentary says, about this collect, that:

The Gallican Missale Gothicum includes this as the initial prayer of the first of six Sunday Masses (no. 477); it is the first prayer of the sixth of sixteen Sunday Masses in the Gelasian sacramentary (no. 1198).  The supplement to the Gregorian appoints it (no. 1159) for the eleventh Sunday after (the) Pentecost (octave), and the Sarum missal and previous Prayer Books for the eleventh Sunday after Trinity.  It has undergone several revisions.  The 1549 version reads:

God, which declarest thy almighty power, most chiefly in showing mercy and pity; Give unto us abundantly thy grace that we, running to thy promises, may be made partakers of thy heavenly treasure; through Jesus Christ our Lord.

The words "mercy and pity" would be more literally translated "sparing and showing compassion."  "Give unto us abundantly thy grace" migth be more literally "multiply upon us your grace."

In 1662 the revised petition read:  "Mercifully grant unto us such a measure of thy grace, that we running the way of thy Commandments, may obtain thy gracrious promises, and be made partakers of thy heavenly treasure."  That revision seemed to make the receiving of heavenly treasure a reward for obedience to the commandments rather than a free gift of grace which we pray that we might run forward eagerly to receive.  In the present revision the collect is revised to make it similar to Cranmer's version.  The preamble states with striking force that the supreme demonstration of God's power is shown not in creation and providence, but in His redemptive love and mercy.

Here's a link to the Missale Gothicum at archive.org.

About the Missale Gothicum of the Gallican Rite:

The Missale Gothicum (Vatican, Queen Christina MSS. 317), described by Delisle, No. 3, is a manuscript dating from the end of the seventh century and once belonging to the Petau Library. The name is due to a fifteenth-century note at the beginning of the book, and hence it has been attributed by Tommasi and Mabillon to Narbonne, which was in the Visigothic Kingdom. Duchesne, judging by the inclusion of Masses for the feasts of St. Symphorian and St. Léger (d. 680), attributes it to Autun. The Masses are numbered, the MS. beginning with Christmas Eve, which is numbered "III". Probably there were once two Advent Masses, as in the "Missale Gallicanum". There are eighty-one numbered sections, of which the last is the first prayer of "Missa Romensif cottidiana", with which the MS. breaks off. The details of the Masses in this book are given in the section of the present article on the liturgical year. The Masses are all Gallican as to order, but many of the actual prayers are Roman. The "Missale Gothicum" has been printed by Tommasi (Codices Sacramentorum, Rome, 1680), Mabillon (De Liturgiâ Gallicanâ, Paris, 1685), Muratori (Liturgia Romana Vetus, Venice, 1748), Neale and Forbes (op. cit.), and Migne's "Patrologia Latina" (Vol. LXXII).

And then, at the Offertory: