य ते हेतिर्मीढुष्टम हस्ते बभुवे धनुः।

तयाऽस्मान् विश्वतस्त्वमयक्ष्म्या  परिब्भुज॥

ya te hetirmīḍhuṣṭama haste babhuve dhanuḥ |

tayā'smān viśvatastvamayakṣmyā  paribbhuja || (1:13)

Meaning:

O the bountiful one! Please protect us from all diseases and all evil effects with your hands and the weaponries in your hands.

Notes:

Recitation of this mantra protects us from enemies. It is important to note that many of the mantras have effect on our wellbeing. That is why, Śrī Rudram is considered as very auspicious and is capable of resolving all our problems. Hence so much importance is given to Śrī Rudram.

This mantra addresses Him as the bountiful one, who always showers His Grace and Blessings on us due to our prayers. Again prayer in this mantra is for universal wellbeing. It is a prayer to protect us from all sorts of health issues and against enemies. Enemies are two types. One is external and another is internal. In those days, warriors in a battle are called enemies. Internally, negativities are considered as enemies. Each of us have ethereal body and negativities cause a deep dent in our ethereal bodies causing manifestation of physical ailments. Protection is sought from Him against psychological enemies as well as negative forces. Ayakṣma means healthy. In short, this mantra seeks His protection from both external evil influences and sickness and disease.

After fearing for His bow and arrows, we gradually become closer to Him through prayers. This is further explained in the next two mantras here.

Kṛṣṇa says in Bhagavad Gītā (III.37), “It is desire begotten of the element of rajas which appears as wrath; it is insatiable and wicked. Know this to be your enemy.”

नमस्ते अस्त्वायुधायानातताय धृष्णवे।

उभाभ्याम् उत ते नमो बाहुभ्यां तव धन्वने॥

namaste astvāyudhāyānātatāya dhṛṣṇave |

ubhābhyām uta te namo bāhubhyāṁ tava dhanvane || (1:14)

Meaning:

O Rudra! We salute your weapons that have become ineffective (due to our prayers, you have made them ineffective). Still we know that they are capable of destruction. We offer our salutations to your two hands and your bow (and also arrows; quiver is implied).

Notes:

Rudra is always considered as ferocious and terrifying. Through persistent prayers to His weaponries and His hands and to Him directly, all His ferocious qualities are subdued and now He is ready to shower His Grace on us. But at the same time, we are aware that He can destroy the sinner in no time, though He is appearing auspicious as of now. By offering prayers to Him, we seek all-round protection from Him. Now, we know that He will not hesitate to destroy us, if by chance we indulge in adharma (unrighteousness, injustice, irreligion, wickedness).

परि ते धन्वनो हेतिरस्मान् वृणक्तु विश्वतः।

अथो य इषुधिस्तवारे अस्मन्नि धेहि तम्॥

pari te dhanvano hetirasmān vṛṇaktu viśvataḥ |

atho ya iṣudhistavāre asmanni dhehi tam || (1.15)

Meaning:

Let your arrows of your bow do not disturb us from any directions (because He is omnipresent). You please set apart your quiver for our enemies (both external and internal as discussed previously).

Notes:  

Mantras 13, 14 and 15 are meant to destroy enemies.

With this the first anuvāka containing 15 mantras (ṛcs also written as ṛks which means praise, verse, esp. a sacred verse recited in praise of a deity and verses which were sung and to the Yajus) is concluded.

This anuvāka began by worshipping His weaponries and through repeated prayers, we have made Him auspicious towards us, opposed to His inherent quality of ferociousness. He is not ferocious to everyone. He is not able to control His anger against evil doers and sinners. He does not hesitate to annihilate them. But, through our heartfelt salutations and prayers (He has become auspicious to those who seek Him not only for material benefits, but also for spiritual upliftment and consequent Liberation. Enemies subtly convey our afflicted thoughts processes. Brahman reveals Himself only in a purified mind, hence in spiritual path, all sorts of negative factors should be completely eradicated. The first anuvāka described His form, both ferocious and auspicious. This also goes to prove that He is omnipresent.  

End of anuvāka 1