Now Elihu had waited - Margin, as in Hebrew, expected Job in words. The meaning is plain, that he had waited until all who were older than himself had spoken.
Because they were elder than he - Margin, as in Hebrew, older for days. It appears that they were all older than he was. We have no means of determining their respective ages, though it would seem probable that Eliphaz was the oldest of the three friends, as he uniformly spoke first.

Now Elihu had waited till Job had spoken, because (d) they [were] elder than he.
(d) That is, the three mentioned before.

Now Elihu had waited till Job had spoken,.... Made an end of speaking, until he had thus expressed himself, "the words of Job are ended", Job 31:40, and waited likewise until his three friends had said all they had to say, and which is here supposed and implied, as appears by what follows:
because they were elder than he; it may be added, from the original text, "in", or "as two days" (l); they had lived longer in the world than he, and therefore did not take upon him to speak till they had done; he, as became a young man, was swift to hear, and slow to speak; that they were old men, appears from what Eliphaz says, Job 15:10.
(l) "diebus", Beza, Montanus, Mercerus; "quod ad dies", Schultens.

had spoken--Hebrew, "in words," referring rather to his own "words" of reply, which he had long ago ready, but kept back in deference to the seniority of the friends who spoke.

4-6 And Elihu had waited for Job with words, for they were older than he in days. And Elihu saw that there was no answer in the mouth of the three men, then his wrath was kindled. And Elihu the son of Barachel the Buzite began, and said.
He had waited (perf. in the sense of the plusquamperf., Ew. 135, a) for Job with words (בּדברים as elsewhere בּמלּים, בּמלּין), i.e., until Job should have spoken his last word in the controversial dialogue. Thus he considered it becoming on his part, for they (המּה, illi, whereas אלּה according to the usage of the language is hi) were older (seniores) than he in days (לימים as Job 32:6, less harsh here, instead of the acc. of closer definition, Job 15:10, comp. Job 11:9). As it now became manifest that the friends made no reply to Job's last speeches for want of the right solution of problem, and therefore also Job had nothing further to say, he believes that he may venture, without any seeming want of courtesy, to give utterance to his long-restrained indignation; and Elihu (with Mahpach) the son of Barach'el (Mercha) the Buzite (with Rebia parvum) began and spoke (ויּאמר not with Silluk, but Mercha mahpach., and in fact with Mercha on the accented penult., as Job 3:2, and further).

'Till Job - And his three friends.