Using :joins
SELECT "manuscripts".* FROM "manuscripts" INNER JOIN "timelines" ON timelines.manuscript_id = manuscripts.id WHERE ((timelines.due_date < '2010-05-12') AND (manuscripts.status = 'received'))

Using :include
SELECT "manuscripts"."id" AS t0_r0, "manuscripts"."title" AS t0_r1, "manuscripts"."msid" AS t0_r2, "manuscripts"."created_at" AS t0_r3, "manuscripts"."updated_at" AS t0_r4, "manuscripts"."article_type_id" AS t0_r5, "manuscripts"."primary_author_id" AS t0_r6, "manuscripts"."status" AS t0_r7, "manuscripts"."pdf_file_name" AS t0_r8, "manuscripts"."pdf_content_type" AS t0_r9, "manuscripts"."pdf_file_size" AS t0_r10, "manuscripts"."pdf_updated_at" AS t0_r11, "manuscripts"."user_manuscript_history_id" AS t0_r12, "timelines"."id" AS t1_r0, "timelines"."created_at" AS t1_r1, "timelines"."updated_at" AS t1_r2, "timelines"."manuscript_id" AS t1_r3, "timelines"."due_date" AS t1_r4, "timelines"."duration" AS t1_r5 FROM "manuscripts" LEFT OUTER JOIN "timelines" ON timelines.manuscript_id = manuscripts.id WHERE ((timelines.due_date < '2010-05-12') AND (manuscripts.status = 'received'))