I have argued here that Luke is writing to Theophilus the high priest of 37-41CE. Because Luke seems to have priestly interests, I gave the book of Malachi a once-over last night, for it was written against the priests. There seems to be good evidence that Luke uses Malachi at times (aside from the citation of Mal4.6 in Lk1.17).
Luke 18 particularly is shot through with allusions of Malachi 3.5, which reads thus:
"Then I will draw near to you for judgment; I will be a swift witness
against the sorcerers,
against the adulterers,
against those who swear falsely,
against those who oppress the hireling in his wages, the widow, and the orphan,
against those who thrust aside the sojourner,
and those do not fear me,
says the Lord of hosts."
In Luke 18.1-8, we find a defense of WIDOWS and the condemnation of those who NEITHER FEARED GOD nor regarded man. In 18.9-14, we find an implicit denouncement of the Pharisaic haughtiness regarding ADULTERY and EXTORTION. In 18.18-30, we find Jesus reciting the Laws regarding ADULTERY, STEALING, and BEARING FALSE WITNESS.
One cannot help but wonder why Jesus only names the five Laws he names in 18.20. Malachi 1.6 reads, "A son honors his father...." I wonder if this is perhaps why Jesus is including the Law to honor father and mother. (Of course, there is no mention of murder in Malachi, yet Jesus includes the prohibition to kill.) The other Laws mentioned by Jesus find root in Malachi 3.5. I believe Luke's Jesus has Malachi in mind here.
Additionally, the issue of the SOJOURNER is taken up in Luke 10.29-37, the story of the good Samaritan. Defenses of WIDOWS appear in Luke 20.46-47; 21.1-4. SORCERY might be addresed by Jesus in Luke 11.14-26. And the issue of ADULTERY also emerges in Luke 16.18.
Further allusions may be included:
Mal1.6 // Lk6.46
Mal3.1 // Lk7.27 (citation)
Mal4.2 // Lk1.78 (so Marshall, Luke, 94)
Finally, I read somewhere that the Jewish Targum identifies Ezra as the author of Malachi. I must find the reference. Jewish tradition apparently recognized Malachi's relation to Ezra and Nehemiah.