Vellum folio from Roman Psalter containing the sixth responsory of Matins of the Fourth Sunday of Easter in the Roman use (i.e. the third after Easter Octave in OP use).

Psalm 118: 10 text in Latin: All[elu]a. P[salmus] Ne repellas me a mandatis tuis. All[elu]a. All[elu]a. V[ersus]. Benedictus es tu, Domine, doce me iustificationes tuas. P[salmus]. Ne repellas. R[esponsorium] vi. Hymnum cantate nobis, All[elu]a. P[salmus]. Quomodo cantabimus ca[nticum].
Translation:
Alleluia. P[salm (118: 10)] Let me not wander from your commandments, alleluia. V[erse (Ps. 118: 12)]. Blessed be you, O Lord, teach me your statutes. P[salm (118: 10)]. Let me not wander. R[esponsory (Ps 137:3)] 6. Sing for us a song, alleluia. Psalm [137:4]. How shall we sing the song of the Lord.