Fridays of Lent offer the faithful the possibility to receive a plenary indulgence, if they recite the prayer before a crucifix (the indulgence is a partial indulgence any other time).
Also, on any of the Fridays of Lent, one can devoutly recite after Communion the prayer “En ego, O bone et dulcissime Iesus” before a crucifix. From the context, it is imperative to do so after receiving Communion, during thanksgiving, to receive the plenary indulgence.
Prayer Before a Crucifix
EN EGO, O bone et dulcissime Iesu, ante conspectum tuum genibus me provolvo, ac maximo animi ardore te oro atque obtestor, ut meum in cor vividos fidei, spei et caritatis sensus, atque veram peccatorum meorum paenitentiam, eaque emendandi firmissimam voluntatem velis imprimere; dum magno animi affectu et dolore tua quinque vulnera mecum ipse considero ac mente contemplor, illud prae oculis habens, quod iam in ore ponebat tuo David propheta de te, O bone Iesu: Foderunt manus meas et pedes meos: dinumeraverunt omnia ossa mea. Amen.
BEHOLD, O good and most sweet Jesus, I fall upon my knees before Thee, and with most fervent desire beg and beseech Thee that Thou wouldst impress upon my heart a lively sense of faith, hope and charity, true repentance for my sins, and a firm resolve to make amends. And with deep affection and grief, I reflect upon Thy five wounds, having before my eyes that which Thy prophet David spoke about Thee, O good Jesus: “They have pierced my hands and feet, they have counted all my bones.” Amen.