The fourth Sukta from the first mandala of the Rigveda is dedicated to Devraj Indra. His sage is Madhuchchhanda. The verses used in these are Gayatri. Here is a compilation of total 10 mantras which are given below with their explanation.
Through this mantra, Rishi Indra is demanding cow wealth from God. They say – Hey Sompayee Indra! You come to our yagya to drink Som and after taking Som, being happy, give cows etc. money to us petitioners.
अथा ते अन्तमानां विद्याम सुमतीनाम्। मा नो अतिख्य आ गहि ॥ 3 ॥
Sage says – Hey Indra! May we gain more and more knowledge about you by being in the presence of the best wise men who are closer to you. You also don’t reveal your form in front of anyone other than us.
Sage says – O wise man! You go near Indra, the undefeated, executive, with special intelligence and get wealth and prosperity for the sake of friends and relatives.
Sage says – O Indra by your grace! May we get all the glory etc., so that whatever enemy or friend sees us, they consider us fortunate. Emashumashve bhar yagyaashriya nrimadanam.
एमाशुमाशवे भर यज्ञश्रियं नृमादनम् । पतयन् मन्दयत्सखम् ॥ 7 ॥
Sage say – dedicate Som to the fast-moving Indra who beautifies the Yagya, gives joy, gives happiness, completes the Yagya and makes the relatives happy.
Sage says – O Indra who performs hundreds of Yagya! You have become the destroyer of the demons by becoming strong with this som leaf. With this power, you are the protector of the warriors in the battlefield.
Sage says – the one who is the protector of wealth everywhere, the destroyer of troubles and the one who has a sense of friendship with Yagyikas, sing hymns to that Indra.
Note – If the fourth hymn of the first circle is read carefully, then it can be understood that their sage is only Madhuchchhanda and here all the mantras are dedicated to Indra. We can probably assume that Rishi Madhuchchhanda must have been the foremost worshiper of Devraj Indra.