אֵין הַמִּצְוָה נִקְרֵאת אֶלָּא עַל שֵׁם גּוֹמְרָהּ

ביטוי (אנגלית)

A commandment is called only by the name of the one who completes it

הגדרה (אנגלית)

The fulfillment of the commandment is attributed to the person who actually completes it. The 'credit' goes to the one who finishes its performance.

("The whole commandment—if you have begun a commandment, be sure to complete all of it... Rabbi Yohanan said: Whoever begins a commandment and then another comes and completes it, the commandment is called by the name of the one who completes it"—Midrash Tanchuma (Warsaw), Parshat Ekev, section 6; and: "A commandment is called only by the name of the one who completes it"—Mesilat Yesharim, chapter 7)