Reading the Didache for the first time, I was struck by many similarities between it and Matthew (particularly the Sermon on the Mount section). For instance, this is from the first chapter of the Didache:
If someone strikes your right cheek, turn to him the other also, and you shall be perfect. If someone impresses you for one mile, go with him two. If someone takes your cloak, give him also your coat. If someone takes from you what is yours, ask it not back, for indeed you are not able.—Didache 1:10-13 (Roberts-Donaldson)
And this is from Matthew:
“You have heard that it was said, ‘An eye for an eye and a tooth for a tooth.’ But I say to you, Do not resist the one who is evil. But if anyone slaps you on the right cheek, turn to him the other also. And if anyone would sue you and take your tunic, let him have your cloak as well. And if anyone forces you to go one mile, go with him two miles. Give to the one who begs from you, and do not refuse the one who would borrow from you.—Matthew 5:38-42 (ESV)
According to Wikipedia:
In modern scholarship a new consensus is emerging which dates the Didache at about the turn of the 2nd Century. At the same time, significant similarities between the Didache and the gospel of Matthew have been found as these writings share words, phrases, and motifs. There is also an increasing reluctance of modern scholars to support the thesis that the Didache used Matthew.
On what basis do scholars reject the dependence of the Didache on Matthew? If there is no dependence, where would the seemingly common teachings have originated? (Note that Wikipedia provides no references for this particular claim.)