Why did Clement and Eusebius believe that Paul was married?

In an answer to a related question ([What is the evidence that suggests that the Apostle Paul was married?](https://christianity.stackexchange.com/a/20410/21576)) , I encountered the following quote from Eusebius: > Clement, indeed, whose words we have just quoted, after the above-mentioned facts gives a statement, on account of those who rejected marriage, of the apostles that had wives. "Or will they," says he, "reject even the apostles? For Peter and Philip begot children; and Philip also gave his daughters in marriage. **And Paul does not hesitate, in one of his epistles, to greet his wife, whom he did not take about with him, that he might not be inconvenienced in his ministry."** ([*Church History*, 3.30](http://www.newadvent.org/fathers/250103.htm) , emphasis added) I'm not aware of any biblical passage where Paul *greets* his wife. The closest thing I can see, given the context, is [1 Corinthians 9:5](https://www.biblegateway.com/passage/?search=1+corinthians+9:5&version=ESV) : > Do we not have the right to take along a believing wife, as do the other apostles and the brothers of the Lord and Cephas? (ESV) But there's nothing here about greeting a wife, or having one at all. Plus, two chapters earlier, he writes: > To the unmarried and the widows I say that it is good for them to remain single as I am. ([1 Co 7:8](https://www.biblegateway.com/passage/?search=1+Corinthians+7:8&version=ESV) , ESV) So what gives? What could Clement/Eusebius have been referring to? A biblical text of which I am unaware? Some early apocryphal work? Is there any tradition, or scholarly opinion, of what text Clement of Alexandria is referring to?