Exodus 12:28

וילכו ויעשו בני ישראל AND THE CHILDREN OF ISRAEL WENT AND DID — But did they really do this at once — was not all this spoken to them at the beginning of the month (cf. Rashi on v. 3) and they carried out the command only on the tenth and the fourteenth? But the explanation is: so soon as they had taken these duties upon themselves Scripture accounts it unto them as though they had already performed them (Mekhilta). וילכו ויעשו THEY WENT AND DID — Scripture enumerates their going also, to give them a reward for going and a reward for doing (Mekhilta). כאשר צוה ה' את משה ואהרן [THEY DID] AS THE LORD HAD COMMANDED MOSES AND AARON — This is stated for the purpose of declaring Israel’s praise — that they did not omit a single matter of all the commandments of Moses and Aaron. And what is the meaning of כן עשו SO DID THEY? Moses and Aaron also did thus!(Mekhilta).

וַיֵּלְכ֥וּ וַֽיַּעֲשׂ֖וּ בְּנֵ֣י יִשְׂרָאֵ֑ל כַּאֲשֶׁ֨ר צִוָּ֧ה יְהֹוָ֛ה אֶת־מֹשֶׁ֥ה וְאַהֲרֹ֖ן כֵּ֥ן עָשֽׂוּ׃ {ס}        

And the children of Yisra᾽el went away, and did as the Lord had commanded Moshe and Aharon, so they did.