Canto 1 - Boyhood
Bāla-kāṇḍa
Chapter 27: Viśvāmitra Teaches Rāma to Summon Divine Weapons
Text 1.27.6

वज्रमस्त्रं वरश्रेष्ठ शैवं शूलवरं तथा।
अस्त्रं ब्रह्मशिरश्चैव ऐषीकम् अपि राघव।
ददामि ते महाबाहो ब्राह्ममस्त्रमनुत्तमम्॥

vajram astraṁ vara-śreṣṭha śaivaṁ śūla-varaṁ tathā
astraṁ
brahma-śiraś caiva aiṣīkam api rāghava
dadāmi
te mahā-bāho brāhmam astram anuttamam

vajram astram = the Vajra weapon; vara-śreṣṭha = O best of excellent persons; śaivam = the Śaiva weapon; śūla-varam tathā = the best of tridents; astram brahma-śiraḥ ca eva = the Brahma-śirā weapon; aiṣīkam api = the Aiṣīka; rāghava = Rāghava; dadāmi = I will give; te = You; mahā-bāho = O mighty-armed; brāhmam astram = weapon of Brahmā; anuttamam = and the excellent.

O mighty-armed Rāghava, O best of excellent persons, I will give You the Vajra weapon, the Śaiva weapon, the best of tridents, the Brahma-śirā weapon, the Aiṣīka and the excellent weapon of Brahmā.

The Brahma-śirā is different from the Brahmāstra, the weapon of Brahmā.