וַיֹּ֗אמֶר אַל־תִּשְׁלַ֤ח יָֽדְךָ֙ אֶל־הַנַּ֔עַר וְאַל־תַּ֥עַשׂ ל֖וֹ מְא֑וּמָּה כִּ֣י ׀ עַתָּ֣ה יָדַ֗עְתִּי כִּֽי־יְרֵ֤א אֱלֹהִים֙ אַ֔תָּה וְלֹ֥א חָשַׂ֛כְתָּ אֶת־בִּנְךָ֥ אֶת־יְחִידְךָ֖ מִמֶּֽנִּי׃
Ia berkata, “Jangan ulurkan tanganmu kepada anak itu, dan jangan berbuat apa pun kepadanya. Sebab sekarang Aku tahu bahwa engkau takut akan Allah, karena engkau tidak menahan anakmu, anakmu yang tunggal, dari-Ku.”
Rashi
אל תשלח LAY NOT THINE HAND [UPON THE LAD] to slay him. Then he (Abraham) said to God, “If this be so, I have come here for nothing; let me at least inflict a wound on him and draw some blood from him”. God replied, “Neither do thou anything (מאומה) to him” — inflict no blemish (מום) on him (Genesis Rabbah 56:7).
Bekhor Shor
Do not stretch out your hand against the lad: For you have already done the commandment. As He only commanded you to bring him up, and you brought him up over the wood.
Chizkuni
עתה ידעתי, “now I know for a fact, etc;” did G-d not already know? Actually the meaning is: “now I am able to make My knowledge public to all.” We have a similar formulation in Exodus 32,12, where G-d said to Moses: ידעתיך בשם, “I have made your name well known.” The appropriate translation would be: “I have made you so famous that no one can dispute it.”