כִּ֣י ׀ אַתָּ֣ה אֱלֹהַ֗י גָּלִ֙יתָ֙ אֶת־אֹ֣זֶן עַבְדְּךָ֔ לִבְנ֥וֹת ל֖וֹ בָּ֑יִת עַל־כֵּן֙ מָצָ֣א עַבְדְּךָ֔ לְהִתְפַּלֵּ֖ל לְפָנֶֽיךָ׃
Porque tú, Dios mío, revelaste al oído á tu siervo que le has de edificar casa; por eso ha hallado tu siervo motivo de orar delante de ti.
Rashi
For You, my God, have revealed It is surely fitting for You to cause Your words to be realized, for You Yourself revealed to [my] ear to build me a house, as it is written: (v. 10): “and I told you and the Lord will build you a house.”
Rashi
therefore, Your servant has found [occasion] to pray before You i.e., If You Yourself had not promised me to bring upon my seed these favors, it would not enter my mind to make supplication, for who am I that You have brought even this far, but since You said for Your sake to bring me all these favors, I therefore pray that You cause Your words to be realized.