diff --git a/velox/connectors/hive/FileHandleKey.h b/velox/connectors/hive/FileHandleKey.h
index 0a69d835cf628..24ce3b8fcb60a 100644
--- a/velox/connectors/hive/FileHandleKey.h
+++ b/velox/connectors/hive/FileHandleKey.h
@@ -61,6 +61,8 @@ class FileHandleKey {
 template <class T>
 inline void hash_combine(std::size_t& seed, const T& v) {
   std::hash<T> hasher;
+  // See boost::hash_combine
+  // https://www.boost.org/doc/libs/1_55_0/doc/html/hash/reference.html#boost.hash_combine
   seed ^= hasher(v) + 0x9e3779b9 + (seed << 6) + (seed >> 2);
 }