Retrieval-Augmented Generation is a powerful method for enhancing language models (LMs), but existing retrieval techniques are limited.Embedding-based methods are often inaccurate due to their reliance on lexical similarity, while neural retrievers are computationally expensive to train.To overcome these issues, we introduce You Only Use Reactive Attention slice (YOURA), a training-free and fine-tuning-free attention-based retrieval technique. When retrieving, YOURA uses a novel reaction score heuristic, which quantifies how an LM’s self-attention “reacts” to a user query. We also propose a sentence extraction algorithm to efficiently preprocess the context.Evaluations on three open-source LMs using the LongBench and BABILong datasets show YOURA’s effectiveness. Our framework improves QA task accuracy by up to 15% and inference throughput by up to 31% compared to embedding-based retrieval.